javascrit Map() code example

Example 1: javascript map function

const posts = [
  { id: 1, title: "Sample Title 1", description: "Lorem ipsum dolor sit amet, consectetur adipiscing elit..." },
  { id: 2, title: "Sample Title 2", description: "Lorem ipsum dolor sit amet, consectetur adipiscing elit..." },
  { id: 3, title: "Sample Title 3", description: "Lorem ipsum dolor sit amet, consectetur adipiscing elit..." },
];
// ES2016+
// Create new array of post IDs. I.e. [1,2,3]
const postIds = posts.map((post) => post.id);
// Create new array of post objects. I.e. [{ id: 1, title: "Sample Title 1" }]
const postSummaries = posts.map((post) => ({ id: post.id, title: post.title }));

// ES2015
// Create new array of post IDs. I.e. [1,2,3]
var postIds = posts.map(function (post) { return post.id; });
// Create new array of post objects. I.e. [{ id: 1, title: "Sample Title 1" }]
var postSummaries = posts.map(function (post) { return { id: post.id, title: post.title }; });

Example 2: map javascript

var numbers = [1, 4, 9];
var doubles = numbers.map(function(num) {
  return num * 2;
});
// doubles is now [2, 8, 18]. numbers still [1, 4, 9]