This question already has answers here:
Explain this javascript code
(1 answer)
JavaScript code trick: What's the value of foo.x
(6 answers)
Multiple assignment confusion
(3 answers)
Closed 3 years ago.
I have this kind of construction
let a = {x: 1}
let b = a
a.x = a = {y: 2}
How you can explain in details how I get these results ?
a.x = undefined
a={y: 2}
b={x: {y: 2}}
Related
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Why can I add named properties to an array as if it were an object?
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Add a property to a JavaScript array
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Closed 27 days ago.
That's my first own question on StackOwerflow.
My problem in JavaScript's arrays is:
var arr=[];
arr[0] = 'a';
arr[1] = 'b';
arr['2']='c';
arr['x']='d';
arr.y='e';
console.log(arr);
[ 'a', 'b', 'c', x: 'd', y: 'e' ] -- this is what i get
And i do not understand what is that actually:
arr['2']='c';
arr['x']='d';
arr.y='e';
I did not expected that behaviour because i've not seen that examples and theory before
This question already has answers here:
Syntax - what does square brackets around a variable declaration mean [duplicate]
(1 answer)
Multiple assignment in JavaScript? What does `[ a, b, c ] = [ 1, 2, 3 ]` mean?
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Javascript. Assign array values to multiple variables? [duplicate]
(2 answers)
Closed 8 months ago.
Consider the declarations of variable "x" and "y"
const x = 1;
const [y] = [1]
What is the meaning of 2nd declaration?
Can someone suggest an article about such declaration type.
This is destructuring assignment.
You are unpacking values from arrays or object properties.
In your above code, a const variable y will be defined with value 1.
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How to determine equality for two JavaScript objects?
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How to explain object references in ECMAScript terms?
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Javascript Object Identities
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If I do:
const o1 = {};
const o2 = {};
is it guaranteed that o1===o2 is false?
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One-liner to take some properties from object in ES 6
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ES6 - Destructuring assignment - Unpack some properties from existing object to a new object? [duplicate]
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Closed 4 years ago.
let x = {
a: 10,
b: 20,
c: 30
};
Is there any way to make only a,b keys of x as another object?
let y = x; //someway here through Object destructing
console.log(y); //{a:10,b:20}
This question already has answers here:
Why does parseInt yield NaN with Array#map?
(8 answers)
Closed 6 years ago.
Since map callback gets called on each element, I would have expected [2,3] as the return value based on the documentation here.
Simply use .map(Number) for this type of task:
var a = ["2", "3"];
var b = a.map(Number);