You don't know destructuring until

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, ES6 (destructuring assignment), - . , , , . . , .

.

const array = [1, 2, 3];
const obj = { x: 4, y: 5, z: 6 };

const a = array[0], b = array[1], c = array[2];
const x = obj.x, y = obj.y, z = obj.z

console.log(a, b, c); // 1 2 3
console.log(x, y, z); // 4 5 6

. ES6.

const array = [1, 2, 3];
const obj = { x: 4, y: 5, z: 6 };

const [ a, b, c ] = array;
const { x, y, z } = obj; 

console.log(a, b, c); // 1 2 3
console.log(x, y, z); // 4 5 6

. , .

const {x, y, z} = obj . const {x: x, y: y, z: z} = obj. , , . x: { x: x, .. }.

target = source target: source, source: target. :

const obj = { x: 4, y: 5, z: 6 };
const { x: X, y: Y, z: Z } = obj;

console.log(X, Y, Z); // 4, 5, 6

X, Y, Z obj.x, obj.y, obj.z . , , . JS- , .

, . , . , , . :

let a, b, c, x, y, z;

[a, b, c] = [1, 2, 3];
({x, y, z} = { x: 4, y: 5, z: 6 });

console.log(a, b, c, x, y, z); // 1 2 3 4 5 6

(), {..} LHS , .

. , . :

//  
const obj = {};
const computedProp = 'z';

[obj.a, obj.b, obj.c] = [1, 2, 3];
({ x: obj.x, y: obj.y, [computedProp]: obj[computedProp] } = { x: 4, y: 5, z: 6 });

console.log(obj.a, obj.b, obj.c); // 1 2 3
console.log(obj.x, obj.y, obj.z); // 4 5 6

//  
let array = [];

({ x: array[0], y: array[1], z: array[2]  } = { x: 4, y: 5, z: 6 });

console.log(array); // [4, 5, 6]

« ?» :

let x = 10, y = 20;

[y, x] = [x, y];

console.log(x, y); // 20 10

. :

const { a: X, a: Y } = { a: 1 };

console.log(X, Y); // 1 1

, ?️.

- /. , :

let a, b, c, x, y, z;

console.log({x, y, z } = { x: 4, y: 5, z: 6 }); // { x: 4, y: 5, z: 6 }
console.log([a, b, c] = [1, 2, 3]); // [1, 2, 3]

, :

let a, b, c, x, y, z;

[a, b] = [c] = [1, 2, 3];
( {x} = {y,z} = {x: 4, y: 5, z: 6} );

console.log(a, b, c); // 1 2 1
console.log(x, y, z); // 4 5 6

[a, b] = [c] = [1, 2, 3] & ( {x} = {y,z} = {x: 4, y: 5, z: 6} ) (.. [c] = [1, 2, 3] [a, b] , {y, z} = {x: 4, y: 5, z: 6} {x}).

, /. :

const [,,c] = [1, 2, 3];
const { y } = { x: 4, y: 5, z: 6 };

console.log(c, y); // 3 5 

, .

rest . :

const [a, ...b] = [1, 2, 3];
const { x, ...y } = { x: 4, y: 5, z: 6 };

console.log(a, b); // 1 [2, 3]
console.log(x, y); // 4 { y: 5, z: 6 }

Rest .

, . :

const { w = 7, x = 8, y, z } = { x: 4, y: 5, z: 6 };
const [ a = 9, b, c, d = 10 ] = [1, 2, 3];

console.log(w, x, y, z); // 7 4 5 6
console.log(a, b, c, d); // 1 2 3 10

/ . .

. :

const { w: WW = 10, x, y, z } = { x: 4, y: 5, z: 6 };

console.log(WW, x, y, z); // 10 4 5 6

, , , :

const array = [ 1, [2, 3, 4], 5 ];

const obj = { 
  x: {
    y: {
      z: 6
    }   
  }
}

const [ a, [ b, c, d ], e ] = array;

const { 
  x: { 
    y: { 
      z: w 
    } 
  } 
} = obj;

console.log(a, b, c, d, e); // 1 2 3 4 5
consoel.log(x); // {y: {z: 6}}
console.log(y) // {z: 6}
console.log(w); // 6

, . :

function baz([x, y]) {
  console.log(x, y);
}

baz([1, 2]); // 1 2
baz([1]); // 1 undefined
baz([, 2]); // undefined 2

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