How do I remove a value from a JSON array? Say I have an array like
var my_array = [3,6,4,8,11]
and I want to remove the number 4 from the array. I have tried delete my_array(4) but that just removes index 4 and apparently it doesn't delete it, it leaves a NULL gap in its place. I simply need to remove the number out of the array entirely. But I don't know at what index that number is positioned so I can't use something like splice.
You must find index of what you need first..
var my_array = [3,6,4,8,11]
var will_delete = my_array.indexOf(4);
my_array.slice(will_delete,1)
Please confusion splice and slice
Splice : https://www.w3schools.com/jsref/jsref_splice.asp
Slice : https://www.w3schools.com/jsref/jsref_slice_array.asp
Related
I generally find indexOf very useful, to get an index directly, and not writing 3-4 lines of for loop to get a match.
Is there any similar function, say like indicesOf , to get an array of all possible matches ?
Or may be having a different name, but acts as a shortcut as beautifully as "indexOf" ?
As you don't mind creating a new Array, you can use the filter() function - it executes a function on each item of the array, then returns a new Array with the items that return true:
// our comparison function
function myCompFunction( element:*, index:int, array:Array ):Boolean
{
return ( element > 10 );
}
var ar:Array = [5,10,15,20];
var ar2:Array = ar.filter( myCompFunction ); // ar2 is now [15,20]
It's not exactly indicies, but then again, you don't need to dereference your objects.
NOTE: because it's calling a function on each element, looping through the array yourself will still be quicker
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/Array.html#filter()
Unfortunately, there is not such shortcut. indexOf works for only one item, and there is no alternative for multiple items.
The solutions are obvious - iterate over the entire array or use some kind of sort on the array. Maybe there are other methods, but they are almost the same - loop through everything and check. Sorry to say it, but that's the way it is :)
I have multiple sub-arrays in one huge array - MasterArray- meaning that the sub-arrays are already INSIDE the MasterArray. I would like to "fuse" all of those sub-arrays - to remove those [ ] square brackets.
I would like to avoid the "concat" method because the arrays are already inside the MasterArray. Is there a command/method how to do this?
Thank you.
var englandCities:Array = [London, Manchester, Leeds];
var franceCities:Array = [Paris, Orleans, Avignon];
var europeanCities:Array = [englandCities, franceCities];
I would like to point let's say...to "London" nested in the europeanCities array somehow.
After I try to trace it, it gives me "englandCities", which makes sense.
trace(europeanCities[0]);
// displays "englandCities"
// how can I make it display "London" ?
How can I make the europeanCities array to display "London" ?
I NEED TO REMOVE THOSE SQUARE BRACES from the "europeanCities" array WITHOUT using the concat() thingie...
OKAY let me rephrase this a bit. My master array:
var europeanCities:Array = [englandCities, franceCities];
equals to
[[London, Manchester, Leeds], [Paris, Orleans, Avignon]];
am I right? And now, how to remove the inner brackets in order to get something like this:
[London, Manchester, Leeds, Paris, Orleans, Avignon];
And please, keep in mind, that the array is much longer than englandCities and frenchCities....there are like...30 different Cities.
You can concat those together easily, and it really is the simplest option:
var englandCities:Array = ["London", "Manchester", "Leeds"];
var frenchCities:Array = ["Paris", "Orleans", "Avignon"];
var masterArray:Array = [englandCities, frenchCities];
var europeanCities:Array = new Array();
for each(var country:Array in masterArray) {
europeanCities = europeanCities.concat(country);
}
trace(europeanCities); // London,Manchester,Leeds,Paris,Orleans,Avignon
I'm not sure I understand your reason for avoiding concat for this, unless the issue is it that you don't want to duplicate the values. (So modifying englandCities[0] will also modify europeanCities[0].)
If your cities are Objects rather than primitive Strings, a concatenated Array will work fine. If they are primitives though, there's no way to do this with an Array. You could however write a function to provide similar behaviour like this:
var englandCities:Array = ["London", "Manchester", "Leeds"];
var frenchCities:Array = ["Paris", "Orleans", "Avignon"];
var allCities:Array = [englandCities, frenchCities];
function europeanCities(id:int):String {
var cityID:uint = 0;
while (id > allCities[cityID].length - 1) {
id -= allCities[cityID].length;
cityID++;
}
return allCities[cityID][id];
}
trace (europeanCities(0)); // London
trace (europeanCities(5)); // Avignon
Create an empty array, then traverse the masterArray taking any sub-arrays, and do a concat() for your new array. This will make you another array that's flat, without disturbing master array.
I just write this here because it is possible.
If you insist on not using concat here is one bad solution:
// join elements into a comma delimited string
var s: String = europeanCities.join(',');
// Split the string with delimiter as commas
europeanCities = s.split(',');
Since the subarray elements automatically will be joined with ',' regardless of join delimiter and our join delimiter is already ',' this will work.
But this solution is cpu intensive and not optimal.
Working with Arrays. I create objects on a Class base, push them into an Array, I have 2 buttons: one adds a Child and pushes it into the Array, second one Shifts Array and removes the Child. Also a function on my mouse, if I click an object, I define it's Array number, remove the Child and... well, not sure if successful but "delete Array[i];" where i is target's Array number. I can see Array.length in a text field every time I do something. Second button actually does remove an object from Array, the number decreases. But deleting a specified object from the Array, as well as Array.slice(i,1), doesn't reduce the Array length. So I'm afraid it may cause overflow. It's only Array, not sure, maybe it's fine to have over a million cells in an Array? Like if I make a game with meteor shower, meteors are removed from the screen, but the Array still has their cells. And if they appear like 30-50 per sec, it's obvious I may get memory problems in 20 minutes of running it. Well it's 60k so maybe I shouldn't worry as only graphics take much memory?
Still, I could use an advice on how to shift an object in a middle of an Array. Chosen one. How do I delete it as if it never was created, same as Shift does? (it does, right?)
Array.splice() will do most of the tricks. As you remove the meteor off screen, you can splice it out of the array, do like this:
var i:int=meteorArray.indexOf(meteorToRemove);
if (i>=0) meteorArray.splice(i,1);
You should not create a new object as a good practice if you are deleting other. Try recycling, or better said 'object pools'
You should figure out the number max of elements you may use at once. create a property 'active' on each and set it to true or false instead of creating/deleting. Then you can run the update on each object and update it only if necessary
For example:
var meteors:Array = [];
// create 500 meteors
for ( var i:int = 0; i < 500; i++ ) {
var meteor:Meteor = new Meteor();
meteor.active = false;
meteors.push(meteor);
}
// enable one meteor
meteors[0].active = true;
// in your update method:
for each (var meteor in meteors )
if ( meteor.active )
meteor.update();
Hope that helps.
Also you can add a helper method to get a meteor available:
function getMeteorAvailable():Meteor
{
for each (var meteor in meteors )
if ( !meteor.active )
return meteor;
}
I want to remove the first four indexes from the array using splice(), then rebuild the array starting at index 0. How do I do this?
Array.index[0] = 'one';
Array.index[1] = 'two';
Array.index[2] = 'three';
Array.index[3] = 'four';
Array.index[4] = 'five';
Array.index[5] = 'six';
Array.index[6] = 'seven';
Array.index[7] = 'eight';
Array.splice(0, 4);
Array.index[0] = 'five';
Array.index[1] = 'six';
Array.index[2] = 'seven';
Array.index[3] = 'eight';
I am accessing the array via a timer, on each iteration I want to remove the first four indexes of the array. I assumed splice() would remove the indexes then rebuild the array starting at 0 index. it doesn't, so instead what I have done is created a 'deleteIndex' variable, on each iteration a +4 is added to deleteIndex.
var deleteIndex:int = 4;
function updateTimer(event:TimerEvent):void
{
Array.splice(0,deleteIndex);
deleteIndex = deleteIndex + 4;
}
What type of object is "Array" in the code you have shown? The Flash Array object does not have a property named "index". The Array class is dynamic, which means that it let's you add random properties to it at run time (which seems to be what you are doing).
In any case, if you are using the standard Flash Array class, it's splice() method updates the array indexes automatically. Here is a code example that proves it:
var a:Array = [1,2,3,4,5];
trace("third element: ", a[2]); // output: 3
a.splice(2,1); // delete 3rd element
trace(a); // output: 1,2,4,5
trace(a.length); // ouput: 4
trace("third element: ", a[2]); // output: 4
If I am understanding what you want correctly, you need to use the unshift method of Array.
example :
var someArray:Array = new Array(0,1,2,3,4,5,6,7,8);
someArray.splice(0,4);
somearray.unshift(5,6,7,8);
Also, you are using the Array Class improperly, you need to create an instance of an array to work with first.
The question is confusing because you used Array class name instead of an instance of an array. But as the commenter on this post said, if you splice elements, it automatically re-indexes.
im not sure what you want to do, but Array=Array.splice(0,4) should fix somethin..
I have created an empty json object having an array itemlist(which further contains itemid and title of an item) by this:
var jsonObj = {};
jsonObj.itemlist=[];
jsonObj.itemlist.push({});
Firstly, have i done the declaration correctly?
Secondly, the title and itemid are generated dynamically so i need to add them to the itemlist array. I tried this but it keeps only one array element:
jsonObj.itemlist['title']=gentitle;
jsonObj.itemlist['itemid']=genitemid;
How can i add multiple elements (not all at once) if i have an empty array of itemlists?
Also, i also need to remove a particular array element based on the title of the element. How can that be done? I think the splice and delete function can be used for this, but how can i find the index of that element?
since you already pushed a empty object into the array, you need to modify that object:
jsonObj.itemlist[0]['title']=gentitle;
jsonObj.itemlist[0]['itemid']=genitemid;
To add more objects, you can do the same thing: push in an empty object, then modify that object. Or, you can create an object, modify it, then push it into the list.
var new_obj = {'title':gentitle, 'itemid':genitemid};
jsonObj.itemlist.push( new_obj );
To delete objects with certain attribute value:
for (var i = jsonObj.itemlist.length-1; i >= 0; i--)
if(jsonObj.itemlist[i]['title'] == "to-be-removed")
jsonObj.itemlist.splice(i,1);
Note that you need to go backward, otherwise the splice will mess up the array indexes