I'm getting a destructure lint error and, more broadly, trying to understand hot destructure different types of objects.
I'm not sure why this needs to be destructured, or what the destructured syntax would be:
let displayUrl = websiteUrl.split('/')[0];
This is the syntax to destructure an array.
let [displayUrl] = websiteUrl.split('/');
Or if you are expecting more parts after splitting the string:
let [part1, part2, part3] = websiteUrl.split('/');
Using destructuring synxtax is useful for keeping the code shorter when there are multiple parts that needs to be assigned to variables. for example:
Instead of writing as
const firstElem = elements[0];
const secondElem = elements[1];
const thirdElem = elements[2];
const fourthElem = elements[3];
Using destructing syntax, you can achieve the same result by
const [firstElem, secondElem, thirdElem, fourthElem] = elements;
In your case where there is only element, I don't think there is any difference.
Related
I am working on a discord bot written in nodejs, the bot utilises a mysql database server to store information. The problem I have run into is that I cannot seem to retrieve the data from the database in a neat way, every single thing I try seems to run into some issue or another.
The select query returns an object called RowDataPacket. When googling every single result will reference this solution: Object.values(JSON.parse(JSON.stringify(rows)))
It postulates that I should get the values back, but I dont I get an array back that is as hard to work with as the rowdatapacket object.
This is a snippet of my code:
const kenneledMemberRolesTableName = 'kenneled_member_roles'
const kenneledMemberKey = 'kenneled_member'
const kenneledMemberRoleKey = 'kenneled_member_role_id'
const kenneledStaffMemberKey = 'kenneled_staff_member'
const kenneledDateKey = 'kenneled_date'
const kenneledReturnableRoleKey = 'kenneled_role_can_be_returned'
async function findKenneledMemberRoles(kenneledMemberId) {
let sql = `SELECT CAST(${kenneledMemberRoleKey} AS Char) FROM ${kenneledMemberRolesTableName} WHERE ${kenneledMemberKey} = ${kenneledMemberId}`
let rows = await databaseAccessor.runQuery(sql)
let result = JSON.parse(JSON.stringify(rows)).map(row => {
return row.kenneled_member_role_id
})
return result
}
This seemed to work, until I had to do a type conversion on the value, now the dot notations requires me to reference row.CAST(kenneled_member_role_id AS Char), this cannot work, and I have found no other way to retrieve the data than through dot notation. I swear there must be a better way to work with mysql rowdatapackets but the solution eludes me
I figured out something that works, however I still feel like this is an inelegant solution, I would love to hear from others if I am misunderstanding how to work with mysql code in nodejs, or if this is just a consequence of the library:
let result = JSON.parse(JSON.stringify(rows)).map(row => {
return row[`CAST(${kenneledMemberRoleKey} AS CHAR)`];
})
So what I did is I access the value through brackets instead of dot notation, this seems to work, and at least makes me able to store part of or the whole expression in a constant variable, hiding the ugliness.
i am trying to do assertion on a json. basically i have to compare two json:
cy.get('h4#idParameters').each(($e, index, $list) => {
const text = $e.text()
expect(text).to.eq(parameters)
})
but I get the following error:
in the assertion if I use "contain" instead of "eq" the result doesn't change
There exist a space after ":" char in the first parameter. These strings are not equal.
If you want to compare this as a string, ensure it does not have extra spaces, points, or is in a different order.
But the better approach is to compare as JSON. One interesting approach should be using the deep-equal-in-any-order plugin. This plugin compares objects independent of it order. But first ensure to transform JSON strings to objects.
in the end I solved it like this. Thanks for the advice #Erme.
cy.get('h4#idParameters').each(($e, index, $list) => {
const text = $e.text()
var p1 = JSON.stringify(text)
var p2 = JSON.stringify(parameters)
p1=p1.replace(/\s/g, '');
p2=p2.replace(/\s/g, '');
p2 = p2.substr(1,p2.length)
expect(p1).to.contain(p2)
})
I learning ES6 and try to use new for me endsWith. Before this I used includes in some of my scripts, and I thought that mechanic will be same. I picked a casual task: I have domains list and want to filter all "cn" domains. Logic is:
let ends = [".cn",".tw",".jp"]
for(let i=0;i<arrayOfDomains.length;i++){
const host = /https?:\/\/(www\.)?([a-zA-Z0-9-]+\.)+[a-zA-Z0-9]+/.exec(arrayOfDomains[i])[0];
console.log(host.endsWith(ends))
}
and result of console.log all false. Is there a way to use array in endsWith?
No, there isn't a way to use an array in endsWith, one option is to declare another function that uses the ends array and host variable as parameters to check it.
You can try something like this:
let ends = [".cs", ".com"];
let host = "www.page.com";
let hostEndsWith = (host, ends) => {
let value = false;
value = ends.some(element => {
return host.endsWith(element);
});
console.log(value);
};
hostEndsWith(host, ends);
You can copy that code in JSFiddle to test it.
Here is the information about the endsWith function endsWith informartion
I hope this helps you!
My goal is to create some kind of Parser to parse string formulas, similar to Excel formulas.
Formula string example (barcode example) -
"CONCAT('98', ZEROFILL([productNumber],5,'0'), ZEROFILL(EQUATION([weightKG]*1000),5,'0'))"
where
'98' - String
[productNumber] and [weightKG] - are variables that can be changed
CONCAT, ZEROFILL and EQUATION are methods which exist in class
For this formula with variables [productNumber] = '1' and [weightKG] = 0.1 result must be
'980000100100'
The question is how to split/parse whole string to parts and detect methods, variables and string values?
Another idea occurred, while i was typing - is to store whole formula in XML format.
Thank You.
You can use String.split() to get an array of substrings.
However, using your example, calling split(",") would give you the following array:
[0]=CONCAT('98'
[1]= ZEROFILL([productNumber]
[2]=5
[3]='0')
[4]= ZEROFILL(EQUATION([weightKG]*1000)
[5]=5
[6]='0'))
That doesn't seem like it will be very helpful for your project. Instead, you might think about creating a parse() function with some logic to find useful substrings:
function parse(input:String):Array {
var firstParen:int = input.indexOf("(");
var lastParen:int = input.lastIndexOf(")");
var formulaName:String = input.substring(0, firstParen);
var arguments:String = input.substring(firstParen, lastParen);
var argumentList:Array = parseArgs(arguments);
var result:Array = new Array();
result.push(formulaName);
//Recursively call parse() on the argumentList
foreach (var elem:* in argumentList) {
result.push(elem); //Could be string or array.
}
}
function parseArgs(input:String):Array {
// Look for commas that aren't enclosed inside parenthesis and
// construct an array of substrings based on that.
//A regex may be helpful here, but the implementation is left
//as an exercise for the reader.
}
I will run a set of experiments. The main method evaluated has the following signature:
[Model threshold] = detect(...
TrainNeg, TrainPos, nf, nT, factors, ...
removeEachStage, applyEstEachStage, removeFeatures);
where removeEachStage, applyEstEachStage, and removeFeatures are booleans. You can see that if I reverse the order of any of these boolean parameters I may get wrong results.
Is there a method in MATLAB that allows better organization in order to minimize this kind of error? Or is there any tool I can use to protect me against these errors?
Organization with a struct
You could input a struct that has these parameters as it's fields.
For example a structure with fields
setts.TrainNeg
.TrainPos
.nf
.nT
.factors
.removeEachStage
.applyEstEachStage
.removeFeatures
That way when you set the fields it is clear what the field is, unlike a function call where you have to remember the order of the parameters.
Then your function call becomes
[Model threshold] = detect(setts);
and your function definition would be something like
function [model, threshold] = detect(setts)
Then simply replace the occurrences of e.g. param with setts.param.
Mixed approach
You can also mix this approach with your current one if you prefer, e.g.
[Model threshold] = detect(in1, in2, setts);
if you wanted to still explicitly include in1 and in2, and bundle the rest into setts.
OOP approach
Another option is to turn detect into a class. The benefit to this is that a detect object would then have member variables with fixed names, as opposed to structs where if you make a typo when setting a field you just create a new field with the misspelled name.
For example
classdef detect()
properties
TrainNeg = [];
TrainPos = [];
nf = [];
nT = [];
factors = [];
removeEachStage = [];
applyEstEachStage = [];
removeFeatures =[];
end
methods
function run(self)
% Put the old detect code in here, use e.g. self.TrainNeg to access member variables (aka properties)
end
end