Example 1: javascript map array
const myArray = ['Sam', 'Alice', 'Nick', 'Matt'];
// Appends text to each element of the array
const newArray = myArray.map(name => {
return 'My name is ' + name;
});
console.log(newArray); // ['My name is Sam', 'My Name is Alice', ...]
// Appends the index of each element with it's value
const anotherArray = myArray.map((value, index) => index + ": " + value);
console.log(anotherArray); // ['0: Sam', '1: Alice', '2: Nick', ...]
// Starting array is unchanged
console.log(myArray); // ['Sam', 'Alice', 'Nick', 'Matt']
Example 2: 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 3: javascript map
array.map((item) => {
return item * 2
} // an example that will map through a a list of items and return a new array with the item multiplied by 2
Example 4: maps in javascript
// Map decalaration in javaScript
const obj1 = { name: 'ismail' };
const obj2 = { name: 'sulman' };
const obj3 = { name: 'naeem' };
firstMap = new Map([
[
[obj1, [{ date: 'yesterday', price: '10$' }]], // using object as a key in the map and object inside the array
[obj2, [{ date: 'today', price: '100$' }]]
]
]);
firstMap.set(obj3, [{ date: "yesterday", price: '150$' }]); //pushing the obj to the Map
// iterating the Map
for (const entry of firstMap.entries()) {
console.log(entry);
};
console.log(firstMap);
firstMap.delete(obj3);
console.log(firstMap);
Example 5: javascript map function
/* Answer to: "javascript map function" */
/*
<Array>.map() - One of the most useful in-built methods in JavaScript (imo).
The map() method creates a new array populated with the results of calling
a provided function on every element in the calling array.
For more information, click on the source link.
Let me make some examples of it's uses:
*/
let array = [1, 4, 9, 16];
array.map(num => num * 2); // [2, 8, 18, 32];
array.map(pounds => `£${pounds}.00`); // ["£1.00", "£4.00", "£9.00", "£16.00"];
array.map(item => Math.sqrt(item)); // [1, 2, 3, 4];
Example 6: 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]