Related
Is there an elegant way to access the first property of an object...
where you don't know the name of your properties
without using a loop like for .. in or jQuery's $.each
For example, I need to access foo1 object without knowing the name of foo1:
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
var obj = { first: 'someVal' };
obj[Object.keys(obj)[0]]; //returns 'someVal'
Object.values(obj)[0]; // returns 'someVal'
Using this you can access also other properties by indexes. Be aware tho! Object.keys or Object.values return order is not guaranteed as per ECMAScript however unofficially it is by all major browsers implementations, please read https://stackoverflow.com/a/23202095 for details on this.
Try the for … in loop and break after the first iteration:
for (var prop in object) {
// object[prop]
break;
}
You can also do Object.values(example)[0].
You can use Object.values() to access values of an object:
var obj = { first: 'someVal' };
Object.values(obj)[0]; // someVal
Use Object.keys to get an array of the properties on an object. Example:
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
var keys = Object.keys(example); // => ["foo1", "foo2", "foo3"] (Note: the order here is not reliable)
Documentation and cross-browser shim provided here. An example of its use can be found in another one of my answers here.
Edit: for clarity, I just want to echo what was correctly stated in other answers: the key order in JavaScript objects is undefined.
A one-liner version:
var val = example[function() { for (var k in example) return k }()];
There isn't a "first" property. Object keys are unordered.
If you loop over them with for (var foo in bar) you will get them in some order, but it may change in future (especially if you add or remove other keys).
The top answer could generate the whole array and then capture from the list. Here is an another effective shortcut
var obj = { first: 'someVal' };
Object.entries(obj)[0][1] // someVal
Solution with lodash library:
_.find(example) // => {name: "foo1"}
but there is no guarantee of the object properties internal storage order because it depends on javascript VM implementation.
Here is a cleaner way of getting the first key:
var object = {
foo1: 'value of the first property "foo1"',
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
let [firstKey] = Object.keys(object)
console.log(firstKey)
console.log(object[firstKey])
if someone prefers array destructuring
const [firstKey] = Object.keys(object);
No. An object literal, as defined by MDN is:
a list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).
Therefore an object literal is not an array, and you can only access the properties using their explicit name or a for loop using the in keyword.
To get the first key name in the object you can use:
var obj = { first: 'someVal' };
Object.keys(obj)[0]; //returns 'first'
Returns a string, so you cant access nested objects if there were, like:
var obj = { first: { someVal : { id : 1} }; Here with that solution you can't access id.
The best solution if you want to get the actual object is using lodash like:
obj[_.first(_.keys(obj))].id
To return the value of the first key, (if you don't know exactly the first key name):
var obj = { first: 'someVal' };
obj[Object.keys(obj)[0]]; //returns 'someVal'
if you know the key name just use:
obj.first
or
obj['first']
This has been covered here before.
The concept of first does not apply to object properties, and the order of a for...in loop is not guaranteed by the specs, however in practice it is reliably FIFO except critically for chrome (bug report). Make your decisions accordingly.
I don't recommend you to use Object.keys since its not supported in old IE versions. But if you really need that, you could use the code above to guarantee the back compatibility:
if (!Object.keys) {
Object.keys = (function () {
var hasOwnProperty = Object.prototype.hasOwnProperty,
hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
dontEnums = [
'toString',
'toLocaleString',
'valueOf',
'hasOwnProperty',
'isPrototypeOf',
'propertyIsEnumerable',
'constructor'
],
dontEnumsLength = dontEnums.length;
return function (obj) {
if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) throw new TypeError('Object.keys called on non-object');
var result = [];
for (var prop in obj) {
if (hasOwnProperty.call(obj, prop)) result.push(prop);
}
if (hasDontEnumBug) {
for (var i=0; i < dontEnumsLength; i++) {
if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
}
}
return result;
}})()};
Feature Firefox (Gecko)4 (2.0) Chrome 5 Internet Explorer 9 Opera 12 Safari 5
More info: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/keys
But if you only need the first one, we could arrange a shorter solution like:
var data = {"key1":"123","key2":"456"};
var first = {};
for(key in data){
if(data.hasOwnProperty(key)){
first.key = key;
first.content = data[key];
break;
}
}
console.log(first); // {key:"key",content:"123"}
If you need to access "the first property of an object", it might mean that there is something wrong with your logic. The order of an object's properties should not matter.
A more efficient way to do this, without calling Object.keys() or Object.values() which returns an array:
Object.prototype.firstKey = function () {
for (const k in this) {
if (Object.prototype.hasOwnProperty.call(this, k)) return k;
}
return null;
};
Then you can use it like:
const obj = {a: 1, b: 2, c: 3}
console.log(obj.firstKey()) //=> 'a'
This doesn't necessarily return the first key, see Elements order in a "for (… in …)" loop
we can also do with this approch.
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
Object.entries(example)[0][1];
This is an old question but most of the solutions assume that we know the attribute's name which it is not the case for example if you are trying to visualize data from files that the user can upload or similar cases.
This is a simple function that I use and works in both cases that you know the variable and if not it will return the first attribute of the object (sorted alphabetically)
The label function receives an object d and extract the key if exits, otherwise returns the first attribute of the object.
const data = [
{ label: "A", value: 10 },
{ label: "B", value: 15 },
{ label: "C", value: 20 },
{ label: "D", value: 25 },
{ label: "E", value: 30 }
]
const keys = ['label', 0, '', null, undefined]
const label = (d, k) => k ? d[k] : Object.values(d)[0]
data.forEach(d => {
console.log(`first: ${label(d)}, label: ${label(d, keys[0])}`)
})
keys.forEach(k => {
console.log(`label of ${k}: ${label(data[0], k)}`)
})
For values like 0, '', null, and undefined will return the first element of the array.
this is my solution
const dataToSend = {email:'king#gmail.com',password:'12345'};
const formData = new FormData();
for (let i = 0; i < Object.keys(dataToSend).length; i++) {
formData.append(Object.keys(dataToSend)[i],
Object.values(dataToSend)[i]);
}
console.log(formData);
Any reason not to do this?
> example.map(x => x.name);
(3) ["foo1", "foo2", "foo3"]
Basic syntax to iterate through key-value gracefully
const object1 = {
a: 'somestring',
b: 42
};
for (const [key, value] of Object.entries(object1)) {
console.log(`${key}: ${value}`);
}
// expected output:
// "a: somestring"
// "b: 42"
As others have pointed out, if the order of properties is important, storing them in an object is not a good idea. Instead, you should use an array via square brackets. E.g.,
var example = [ {/* stuff1 */}, { /* stuff2 */}, { /* stuff3 */}];
var first = example[0];
Note that you lose the 'foo' identifiers. But you could add a name property to the contained objects:
var example = [
{name: 'foo1', /* stuff1 */},
{name: 'foo2', /* stuff2 */},
{name: 'foo3', /* stuff3 */}
];
var whatWasFirst = example[0].name;
For those seeking an answer to a similar question, namely: "How do I find one or more properties that match a certain pattern?", I'd recommend using Object.keys(). To extend benekastah's answer:
for (const propName of Object.keys(example)) {
if (propName.startsWith('foo')) {
console.log(`Found propName ${propName} with value ${example[propName]}`);
break;
}
}
I'm using a custom script for importing JSON into Google Sheets through a function. I can import values from propertys without any problem, but I have some problem with a specific array. It is a property which contains more information, but it seems the formatting makes the array into one single value instead of several (something with the slashes?). First, the script:
function getStat(url, propertyName)
{
let content = UrlFetchApp.fetch(url).getContentText();
let parsed = JSON.parse(content);
let processed = parsed.data
.filter(e =>
// Conditions go here:
e.season_format === 'Domestic League' &&
e.season === '2020/2021'
)
.map(e => e.stats[propertyName]);
return processed;
}
I want to get the value after "3" in the array called additional_info (simplified version below). But when I try to get the value, instead I get the third character in the array. I don't get "55" which is the value. I've tried with a bunch of variants. But I can't get it to work. For example, additional_info["3"] returns the third character in the array, not the value. Any tips? I've no problem getting the values of suspended_matches and home_AttackAdvantage.
{
"success": true,
"data": [
{
"season": "2020/2021",
"season_format": "Domestic League",
"stats": {
"suspended_matches": 20,
"homeAttackAdvantage": 3,
"additional_info": "{\"1\":1,\"2\":2,\"3\":55,\"4\"}"
}
}
]
}
The issue was that additional_info is yet another JSON string, so you have to parse it again.
function getStat(url, propertyName, additionalProp)
{
let content = UrlFetchApp.fetch(url).getContentText();
let parsed = JSON.parse(content);
let processed = parsed.data
.filter(e =>
// Conditions go here:
e.season_format === 'Domestic League' &&
e.season === '2020/2021'
)
.map(e => additionalProp
? [
e.stats[propertyName],
JSON.parse(e.stats.additional_info)[additionalProp]
]
: e.stats[propertyName]
);
return processed;
}
This gives you a function you can use in a formula:
=getStat(
"https://api.footystats.org/team?key=example&team_id=93",
"suspended_matches",
"330"
)
If you don't specify the third argument, it will just return a single column.
I'm trying to access a property of an object using a dynamic name. Is this possible?
const something = { bar: "Foobar!" };
const foo = 'bar';
something.foo; // The idea is to access something.bar, getting "Foobar!"
There are two ways to access properties of an object:
Dot notation: something.bar
Bracket notation: something['bar']
The value between the brackets can be any expression. Therefore, if the property name is stored in a variable, you have to use bracket notation:
var something = {
bar: 'foo'
};
var foo = 'bar';
// both x = something[foo] and something[foo] = x work as expected
console.log(something[foo]);
console.log(something.bar)
This is my solution:
function resolve(path, obj) {
return path.split('.').reduce(function(prev, curr) {
return prev ? prev[curr] : null
}, obj || self)
}
Usage examples:
resolve("document.body.style.width")
// or
resolve("style.width", document.body)
// or even use array indexes
// (someObject has been defined in the question)
resolve("part.0.size", someObject)
// returns null when intermediate properties are not defined:
resolve('properties.that.do.not.exist', {hello:'world'})
In javascript we can access with:
dot notation - foo.bar
square brackets - foo[someVar] or foo["string"]
But only second case allows to access properties dynamically:
var foo = { pName1 : 1, pName2 : [1, {foo : bar }, 3] , ...}
var name = "pName"
var num = 1;
foo[name + num]; // 1
// --
var a = 2;
var b = 1;
var c = "foo";
foo[name + a][b][c]; // bar
Following is an ES6 example of how you can access the property of an object using a property name that has been dynamically generated by concatenating two strings.
var suffix = " name";
var person = {
["first" + suffix]: "Nicholas",
["last" + suffix]: "Zakas"
};
console.log(person["first name"]); // "Nicholas"
console.log(person["last name"]); // "Zakas"
This is called computed property names
You can achieve this in quite a few different ways.
let foo = {
bar: 'Hello World'
};
foo.bar;
foo['bar'];
The bracket notation is specially powerful as it let's you access a property based on a variable:
let foo = {
bar: 'Hello World'
};
let prop = 'bar';
foo[prop];
This can be extended to looping over every property of an object. This can be seem redundant due to newer JavaScript constructs such as for ... of ..., but helps illustrate a use case:
let foo = {
bar: 'Hello World',
baz: 'How are you doing?',
last: 'Quite alright'
};
for (let prop in foo.getOwnPropertyNames()) {
console.log(foo[prop]);
}
Both dot and bracket notation also work as expected for nested objects:
let foo = {
bar: {
baz: 'Hello World'
}
};
foo.bar.baz;
foo['bar']['baz'];
foo.bar['baz'];
foo['bar'].baz;
Object destructuring
We could also consider object destructuring as a means to access a property in an object, but as follows:
let foo = {
bar: 'Hello World',
baz: 'How are you doing?',
last: 'Quite alright'
};
let prop = 'last';
let { bar, baz, [prop]: customName } = foo;
// bar = 'Hello World'
// baz = 'How are you doing?'
// customName = 'Quite alright'
You can do it like this using Lodash get
_.get(object, 'a[0].b.c');
UPDATED
Accessing root properties in an object is easily achieved with obj[variable], but getting nested complicates things. Not to write already written code I suggest to use lodash.get.
Example
// Accessing root property
var rootProp = 'rootPropert';
_.get(object, rootProp, defaultValue);
// Accessing nested property
var listOfNestedProperties = [var1, var2];
_.get(object, listOfNestedProperties);
Lodash get can be used in different ways, the documentation lodash.get
To access a property dynamically, simply use square brackets [] as follows:
const something = { bar: "Foobar!" };
const userInput = 'bar';
console.log(something[userInput])
The problem
There's a major gotchya in that solution! (I'm surprised other answers have not brought this up yet). Often you only want to access properties that you've put onto that object yourself, you don't want to grab inherited properties.
Here's an illustration of this issue. Here we have an innocent-looking program, but it has a subtle bug - can you spot it?
const agesOfUsers = { sam: 16, sally: 22 }
const username = prompt('Enter a username:')
if (agesOfUsers[username] !== undefined) {
console.log(`${username} is ${agesOfUsers[username]} years old`)
} else {
console.log(`${username} is not found`)
}
When prompted for a username, if you supply "toString" as a username, it'll give you the following message: "toString is function toString() { [native code] } years old". The issue is that agesOfUsers is an object, and as such, automatically inherits certain properties like .toString() from the base Object class. You can look here for a full list of properties that all objects inherit.
Solutions
Use a Map data structure instead. The stored contents of a map don't suffer from prototype issues, so they provide a clean solution to this problem.
const agesOfUsers = new Map()
agesOfUsers.set('sam', 16)
agesOfUsers.set('sally', 2)
console.log(agesOfUsers.get('sam')) // 16
Use an object with a null prototype, instead of the default prototype. You can use Object.create(null) to create such an object. This sort of object does not suffer from these prototype issues, because you've explicitly created it in a way that it does not inherit anything.
const agesOfUsers = Object.create(null)
agesOfUsers.sam = 16
agesOfUsers.sally = 22;
console.log(agesOfUsers['sam']) // 16
console.log(agesOfUsers['toString']) // undefined - toString was not inherited
You can use Object.hasOwn(yourObj, attrName) to first check if the dynamic key you wish to access is directly on the object and not inherited (learn more here). This is a relatively newer feature, so check the compatibility tables before dropping it into your code. Before Object.hasOwn(yourObj, attrName) came around, you would achieve this same effect via Object.prototype.hasOwnProperty.call(yourObj, attrName). Sometimes, you might see code using yourObj.hasOwnProperty(attrName) too, which sometimes works but it has some pitfalls that you can read about here.
// Try entering the property name "toString",
// you'll see it gets handled correctly.
const user = { name: 'sam', age: 16 }
const propName = prompt('Enter a property name:')
if (Object.hasOwn(user, propName)) {
console.log(`${propName} = ${user[propName]}`)
} else {
console.log(`${propName} is not found`)
}
If you know the key you're trying to use will never be the name of an inherited property (e.g. maybe they're numbers, or they all have the same prefix, etc), you can choose to use the original solution.
I came across a case where I thought I wanted to pass the "address" of an object property as data to another function and populate the object (with AJAX), do lookup from address array, and display in that other function. I couldn't use dot notation without doing string acrobatics so I thought an array might be nice to pass instead. I ended-up doing something different anyway, but seemed related to this post.
Here's a sample of a language file object like the one I wanted data from:
const locs = {
"audioPlayer": {
"controls": {
"start": "start",
"stop": "stop"
},
"heading": "Use controls to start and stop audio."
}
}
I wanted to be able to pass an array such as: ["audioPlayer", "controls", "stop"] to access the language text, "stop" in this case.
I created this little function that looks-up the "least specific" (first) address parameter, and reassigns the returned object to itself. Then it is ready to look-up the next-most-specific address parameter if one exists.
function getText(selectionArray, obj) {
selectionArray.forEach(key => {
obj = obj[key];
});
return obj;
}
usage:
/* returns 'stop' */
console.log(getText(["audioPlayer", "controls", "stop"], locs));
/* returns 'use controls to start and stop audio.' */
console.log(getText(["audioPlayer", "heading"], locs));
ES5 // Check Deeply Nested Variables
This simple piece of code can check for deeply nested variable / value existence without having to check each variable along the way...
var getValue = function( s, context ){
return Function.call( context || null, 'return ' + s )();
}
Ex. - a deeply nested array of objects:
a = [
{
b : [
{
a : 1,
b : [
{
c : 1,
d : 2 // we want to check for this
}
]
}
]
}
]
Instead of :
if(a && a[0] && a[0].b && a[0].b[0] && a[0].b[0].b && a[0].b[0].b[0] && a[0].b[0].b[0].d && a[0].b[0].b[0].d == 2 ) // true
We can now :
if( getValue('a[0].b[0].b[0].d') == 2 ) // true
Cheers!
Others have already mentioned 'dot' and 'square' syntaxes so I want to cover accessing functions and sending parameters in a similar fashion.
Code jsfiddle
var obj = {method:function(p1,p2,p3){console.log("method:",arguments)}}
var str = "method('p1', 'p2', 'p3');"
var match = str.match(/^\s*(\S+)\((.*)\);\s*$/);
var func = match[1]
var parameters = match[2].split(',');
for(var i = 0; i < parameters.length; ++i) {
// clean up param begninning
parameters[i] = parameters[i].replace(/^\s*['"]?/,'');
// clean up param end
parameters[i] = parameters[i].replace(/['"]?\s*$/,'');
}
obj[func](parameters); // sends parameters as array
obj[func].apply(this, parameters); // sends parameters as individual values
I asked a question that kinda duplicated on this topic a while back, and after excessive research, and seeing a lot of information missing that should be here, I feel I have something valuable to add to this older post.
Firstly I want to address that there are several ways to obtain the value of a property and store it in a dynamic Variable. The first most popular, and easiest way IMHO would be:
let properyValue = element.style['enter-a-property'];
however I rarely go this route because it doesn't work on property values assigned via style-sheets. To give you an example, I'll demonstrate with a bit of pseudo code.
let elem = document.getElementById('someDiv');
let cssProp = elem.style['width'];
Using the code example above; if the width property of the div element that was stored in the 'elem' variable was styled in a CSS style-sheet, and not styled inside of its HTML tag, you are without a doubt going to get a return value of undefined stored inside of the cssProp variable. The undefined value occurs because in-order to get the correct value, the code written inside a CSS Style-Sheet needs to be computed in-order to get the value, therefore; you must use a method that will compute the value of the property who's value lies within the style-sheet.
Henceforth the getComputedStyle() method!
function getCssProp(){
let ele = document.getElementById("test");
let cssProp = window.getComputedStyle(ele,null).getPropertyValue("width");
}
W3Schools getComputedValue Doc This gives a good example, and lets you play with it, however, this link Mozilla CSS getComputedValue doc talks about the getComputedValue function in detail, and should be read by any aspiring developer who isn't totally clear on this subject.
As a side note, the getComputedValue method only gets, it does not set. This, obviously is a major downside, however there is a method that gets from CSS style-sheets, as well as sets values, though it is not standard Javascript.
The JQuery method...
$(selector).css(property,value)
...does get, and does set. It is what I use, the only downside is you got to know JQuery, but this is honestly one of the very many good reasons that every Javascript Developer should learn JQuery, it just makes life easy, and offers methods, like this one, which is not available with standard Javascript.
Hope this helps someone!!!
For anyone looking to set the value of a nested variable, here is how to do it:
const _ = require('lodash'); //import lodash module
var object = { 'a': [{ 'b': { 'c': 3 } }] };
_.set(object, 'a[0].b.c', 4);
console.log(object.a[0].b.c);
// => 4
Documentation: https://lodash.com/docs/4.17.15#set
Also, documentation if you want to get a value: https://lodash.com/docs/4.17.15#get
You can do dynamically access the property of an object using the bracket notation. This would look like this obj[yourKey] however JavaScript objects are really not designed to dynamically updated or read. They are intended to be defined on initialisation.
In case you want to dynamically assign and access key value pairs you should use a map instead.
const yourKey = 'yourKey';
// initialise it with the value
const map1 = new Map([
['yourKey', 'yourValue']
]);
// initialise empty then dynamically assign
const map2 = new Map();
map2.set(yourKey, 'yourValue');
console.log(map1.get(yourKey));
console.log(map2.get(yourKey));
demo object example
let obj = {
name: {
first_name: "Bugs",
last_name: "Founder",
role: "Programmer"
}
}
dotted string key for getting the value of
let key = "name.first_name"
Function
const getValueByDottedKeys = (obj, strKey)=>{
let keys = strKey.split(".")
let value = obj[keys[0]];
for(let i=1;i<keys.length;i++){
value = value[keys[i]]
}
return value
}
Calling getValueByDottedKeys function
value = getValueByDottedKeys(obj, key)
console.log(value)
output
Bugs
const getValueByDottedKeys = (obj, strKey)=>{
let keys = strKey.split(".")
let value = obj[keys[0]];
for(let i=1;i<keys.length;i++){
value = value[keys[i]]
}
return value
}
let obj = {
name: {
first_name: "Bugs",
last_name: "Founder",
role: "Programmer"
}
}
let key = "name.first_name"
value = getValueByDottedKeys(obj, key)
console.log(value)
I bumped into the same problem, but the lodash module is limited when handling nested properties. I wrote a more general solution following the idea of a recursive descendent parser. This solution is available in the following Gist:
Recursive descent object dereferencing
Finding Object by reference without, strings,
Note make sure the object you pass in is cloned , i use cloneDeep from lodash for that
if object looks like
const obj = {data: ['an Object',{person: {name: {first:'nick', last:'gray'} }]
path looks like
const objectPath = ['data',1,'person',name','last']
then call below method and it will return the sub object by path given
const child = findObjectByPath(obj, objectPath)
alert( child) // alerts "last"
const findObjectByPath = (objectIn: any, path: any[]) => {
let obj = objectIn
for (let i = 0; i <= path.length - 1; i++) {
const item = path[i]
// keep going up to the next parent
obj = obj[item] // this is by reference
}
return obj
}
You can use getter in Javascript
getter Docs
Check inside the Object whether the property in question exists,
If it does not exist, take it from the window
const something = {
get: (n) => this.n || something.n || window[n]
};
You should use JSON.parse, take a look at https://www.w3schools.com/js/js_json_parse.asp
const obj = JSON.parse('{ "name":"John", "age":30, "city":"New York"}')
console.log(obj.name)
console.log(obj.age)
I am using Redux spread operator to hopefully mantain the state as immutable objects.
However, i am managing to make the most simple unit test fail.
I assume the error probably has to do with immutables, but am i not using the spread operator correctly?
Here is my unit test:
describe('app logic', () => {
it('initialises app', () => {
const newState = reducer(INITIAL_STATE, {type: "NEXT"})
const expectState = {
start: true,
render_component: null,
requests: {},
results: {},
}
console.log('newState', newState)
console.log('expected state', expectState)
expect(newState).to.equal(expectState)
})
})
and here is my reducer
export const INITIAL_STATE = {
start: false,
render_component: null,
requests: {},
results: {}
}
export const next = (state) => {
if (state === INITIAL_STATE) {
return {
...state,
start: true,
}
}
return state
}
export function reducer(state = INITIAL_STATE, action) {
switch (action.type) {
case 'NEXT':
return next(state)
default:
return state
}
}
I print the two objects, and they look the same.
i get the error :
1) app logic initialises app:
AssertionError: expected { Object (start, render_component, ...) } to equal { Object (start, render_component, ...) }
Not sure exactly which testing library you are using, but usually a name like .equal is used to test strict equality ( === ), which means (at least in the case of objects) that the two things being compared must actually reference the exact same object. So, for example,
const original = { a: 1 }; // creates a new object, assign it
const testMe = { a: 1 }; // creates another new object, assign it
console.log( original === testMe ) // false
evaluates to false, because while the objects have the same content, they do not reference the exact same object. They are separate, independently created, objects that happen to have the same content. Compare that to
const original = {a: 1}; // create a new object
const testMe = original; // create another reference to the same object
console.log( original === testMe ); // true
So when you return
return {
...state,
start: true,
}
you are creating and returning a new object, so it naturally can not reference the same object that you created and assigned to the variable name expectedState.
If what you are interested in is not strict equality, but rather just that the content in the two objects are the same, there exists other methods than .equal, usually named something with deep (since they go deep into the objects/arrays/whatever to check if the values are the same).
Chai.js has examples of both expect(x).to.equal(y) and expect(x).to.deep.equal(y) in their docs: http://chaijs.com/api/bdd/#method_equal
Your testing library probably has very similar, if not identical, syntax.
I am using knockout and want to use arrayFilter to return array of objects where a property "modified" inside of another array has value of true.
i.e.
my json object looks like
Family tree
Family{
LastName=Smith
Children{
Name=bob,
Modified=false},
{
Name=tom, Modified=true}
}
Family{
LastName=Jones
Children{
Name=bruno,
Modified=false},
{
Name=mary, Modified=false}
}
The result of the array filter would be (as follows) becuase child tom has modified =true
FamilyTree
Family{
LastName=Smith
Children{
Name=bob,
Modified=false},
{
Name=tom, Modified=true}
}
is this possible?
I think the solution that #pax162 supplied probably answers your question. However, there is the question of usage. The proposed solution is going to perform nested iterations. If you are only expecting to be processing the data once (as opposed to driving some rich client views), this is the approach to take. On the other hand, if you are binding this data to a view, you might consider another more KO-like approach. Here's what I have in mind:
var family = function(data){
var self = {
LastName :ko.observable(data.LastName),
Children : ko.observableArray( data.Children || [])
};
family.hasModifiedChildren = ko.computed(function() {
return ko.utils.arrayFirst(this.Children(),
function(child) {
return child.Modified === true;
}) !== null;
}, family);
return self;
}
Rather than using JSON data, create observable JS objects as such:
var families = return ko.utils.arrayMap(familiesJson, family);
// or, if you need an observable:
families = ko.observableArray(ko.utils.arrayMap(familiesJson, family));
Finally, get your list of families with modified children like this:
var familiesWithModifiedChildren = ko.computed(function() {
return ko.utils.arrayFilter(families, function(fam) {
return fam.hasModifiedChildren();
});
});
If you are building a live-update page, you'll want to go with this style of view model. This will allow Knockout to utilize its observer optimizations rather than building a new array every time the function is evaluated. Hope this helps!
If you want to get only families with at least one modified child, you can do this (http://jsfiddle.net/MAyNn/3/) . The json was not valid, changed it a bit.
var families = [
{
LastName :"Smith",
Children : [{
Name:"bob",
Modified:false},
{
Name:"tom", Modified :true}
]
},
{
LastName :"Jones",
Children : [{
Name:"bruno",
Modified:false},
{
Name:"mary", Modified :false}
]
}
];
var filteredFamilies = ko.utils.arrayFilter(families, function(family){
var hasModified = false;
var first = ko.utils.arrayFirst(family.Children, function(child){
return child.Modified;
})
if (first) {
hasModified = true;
}
return hasModified;
})
console.log(families);
console.log(filteredFamilies);