This question already has answers here:
What is destructuring assignment and its uses?
(3 answers)
What does this symbol mean in JavaScript?
(1 answer)
Javascript object bracket notation ({ Navigation } =) on left side of assign
(5 answers)
Closed 2 years ago.
I've recently came across this particular code:
const arr = [1,2,3];
const { length } = arr;
for (i = 0; i<=length; i++){
console.log(i)
}
Apparently this (const { length } = arr;) somehow works, but I haven't found any information on the Internet on either how or why should this actually work.
My question: how does this { } construction work and why doesn't it work when I change { length } to anything else, like { arrlength }? Can we possibly use this construction with other array's properties and how?
Related
This question already has answers here:
Accessing nested JavaScript objects and arrays by string path
(44 answers)
Access object child properties using a dot notation string [duplicate]
(13 answers)
Closed 7 days ago.
Lets say I have data structured like this
let array = [[1], [2], [3]]
and I want to use those elements as an index:
console.log(matrix[1][2][3])
Is there a way to break out those elements? I am trying to get the logic nailed down for n elements.
Here is what I have:
const getValue = (coords: []) => {
let array = [];
for (let i = 0; i < coords.length; i++) {
array.push([coords[i]]);
}
console.log(complex[array]);
};
But I get the error:
Type 'never[][]' cannot be used as an index type.ts(2538)
This question already has answers here:
Fetching all (javascript) global variables in a page
(5 answers)
Closed 1 year ago.
I am looking for a tool that will display all the values of my variables in a page all all times during execution.
I think that you can just use an object to store your values:
let obj = { var1: 'val1'm var2: 'val2'}
for (let i of Object.keys(obj)) {
console.log(obj[i])
}
Can you provide an example or screen shot on what are you trying to do?
This question already has answers here:
Javascript object bracket notation ({ Navigation } =) on left side of assign
(5 answers)
What is destructuring assignment and its uses?
(3 answers)
Closed 3 years ago.
I know how to declare const variable like const a = 1;
but I dont get what is this
const { app, BrowserWindow } = require('electron')
can anyone explain me?
That’s a destructuring assignment.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
It lets you make shortcuts to members of an array or structure.
This question already has answers here:
How do I check if an array includes a value in JavaScript?
(60 answers)
Check if an element is present in an array [duplicate]
(9 answers)
Closed 4 years ago.
I recently starting learning JS so a beginner level answer would be great! Thanks.
function contains(arr, item) {
// check to see if item is inside of arr
// return true if it is, otherwise return false
}
What about something like this?
const arr = [1,2,3];
const el = 2;
console.log(arr.includes(el)) // true
This question already has answers here:
Javascript object bracket notation ({ Navigation } =) on left side of assign
(5 answers)
ES6 Object Destructuring Default Parameters
(1 answer)
Closed 6 years ago.
I was reading the source for a MeteorJS package (this one) when I came across this:
const {
getMeteorData,
pure = true,
} = expandedOptions;
I did some research to figure out what this code would do, but couldn't find any other instance of const being used like this, or any documentation to clarify it for me.
Any hints, please?
It is using es6 to unpack (or destructure) the values inside the expandedOptions object.
const val = {a:1, b:"hello"};
const {
a,
b
} = val;
console.log(a); //1
console.log(b); //"hello"