js spread parameters

spread operator in javascript

// spread operators can be used for arrays or objects

// cloning to prevent mutation.
let numList = [1,2,3];
let numListClone = [...numList]; // [1, 2, 3]

// spread operator for destructuring.
let animal = {
  name: 'dog',
  color: 'brown',
  age: 7
};
let { age, ...otherProperties } = animal; 

// spread operator as rest operator
function sum(x, y, ...rest) {}

// spread operator for merging arrays or objects
let numLists = [...numList1, ...numList2];
let animalWithBreed = {
  ...animal,
  breed: '',
}

Posted by: Guest on December-03-2020

let arr1 = ['A', 'B', 'C']; let arr2 = ['X', 'Y', 'Z']; let result = [...arr1, ...arr2]; console.log(result); // ['A', 'B', 'C', 'X', 'Y', 'Z'] // spread elements of the array instead of taking the array as a whole

obj = {first_name : "Marty", lovers: ["Jennifer Parker","Baines McFly"] }; let objClone = { ...obj }; // pass all key:value pairs from an object console.log(objClone) // { first_name: "Marty", lovers: ["Jennifer Parker", "Baines McFly"] }

// seperate each element of array using ... let list = ['a','b','c']; let copy = [...list, 'd', 'e']; // ['a', 'b', 'c', 'd', 'e'] //use for infinite parameters to a function function toDoList(...todos) { //todos is an array, so it has map function document.write( `<ul>${todos.map((todo) => `<li>${todo}</li>`).join("")}</ul>` ); } toDoList("wake up", "eat breakfast", ...list); //ul containing: wake up eat breakfast a b c

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