JAVASCRIPT

array map javascript

const array1 = [1, 4, 9, 16];

// pass a function to map
const map1 = array1.map(x => x * 2);

console.log(map1);
// expected output: Array [2, 8, 18, 32]

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

javascript map

const items = [1, 2, 3, 4, 5, 6, 7, 8, 9];

const anotherItems = items.map(item => item * 2);

console.log(anotherItems);

array map

const array1 = [1, 4, 9, 16];

// pass a function to map
const map1 = array1.map(x => x * 2);

console.log(map1);
// expected output: Array [2, 8, 18, 32]

map in an array

let numbers = [33, 22, 44, 55, 66, 77, 88, 99];
const getNumbers = numbers.map(number => number * 2);
console.log(getNumbers);
//Expected output:
/*[
    66,  44,  88, 110,
   132, 154, 176, 198
 ]
 */

array mdn map

let new_array = arr.map(function callback( currentValue[, index[, array]]) {
    // return element for new_array
}[, thisArg])

array to map js

var arr = [
    { key: 'foo', val: 'bar' },
    { key: 'hello', val: 'world' }
];

var result = new Map(arr.map(i => [i.key, i.val]));

// When using TypeScript, need to specify type:
// var result = arr.map((i): [string, string] => [i.key, i.val])

// Unfortunately maps don't stringify well.  This is the contents in array form.
console.log("Result is: " + JSON.stringify([...result])); 
// Map {"foo" => "bar", "hello" => "world"}
 Run code snippet

array map

let numbers = [1, 2, 3, 4]
let filteredNumbers = numbers.map(function(_, index) {
  if (index < 3) {
     return num
  }
})
// index goes from 0, so the filterNumbers are 1,2,3 and undefined.
// filteredNumbers is [1, 2, 3, undefined]
// numbers is still [1, 2, 3, 4]

JS map

const newArray= array.map((data)=> data);

javascript map

const numbers = [0,1,2,3];

console.log(numbers.map((number) => {
  return number;
}));

javascript map

// make new array from edited items of another array
var newArray = unchangedArray.map(function(item, index){
  return item;	// do something to returned item
});

// same in ES6 style (IE not supported)
var newArray2 = unchangedArray.map((item, index) => item);

JavaScript Array Methods .map()

let numbers = [1, 2, 3, 4, 5];
let doubles = numbers.map(number => number * 2)
console.log(doubles)
// --> [ 2, 4, 6, 8, 10 ]

javascript map

const numbers = [2, 4, 6, 8];
const result = numbers.map(a => a * 2);
console.log(result);
//Output: [ 4, 8, 12, 16 ]

array.map

let arr = [1,2,3]

/*
  map accepts a callback function, and each value of arr is passed to the 
  callback function. You define the callback function as you would a regular
  function, you're just doing it inside the map function
  
  map applies the code in the callback function to each value of arr, 
  and creates a new array based on your callback functions return values
*/
let mappedArr = arr.map(function(value){
	return value + 1
})

// mappedArr is:
> [2,3,4]

JavaScript Array map()

const numbers1 = [45, 4, 9, 16, 25];
const numbers2 = numbers1.map(myFunction);

function myFunction(value, index, array) {
  return value * 2;
}

array.map

var x = [1,2,3,4].map( function(item) {return item * 10;});

javascript map

// Creating javascript map with one instruction
const map = new Map([
  ["key", "value"],
  ["key2", "value2"],
]);

array map

function square(arr) {
       const newArr = arr.map(x => x * x );
    return newArr ;
  
  //if you find this answer is useful ,
//upvote ⇑⇑ , so can the others benefit also . @mohammad alshraideh ( ͡~ ͜ʖ ͡°)

JS map

// Arrow function
map((element) => { /* … */ })
map((element, index) => { /* … */ })
map((element, index, array) => { /* … */ })

// Callback function
map(callbackFn)
map(callbackFn, thisArg)

// Inline callback function
map(function(element) { /* … */ })
map(function(element, index) { /* … */ })
map(function(element, index, array){ /* … */ })
map(function(element, index, array) { /* … */ }, thisArg)

.map() method on arrays

arr.map(function(el, i){
return ...
})

javaScript Map() Method

// Create a Map
const fruits = new Map([
  ["apples", 500],
  ["bananas", 300],
  ["oranges", 200]
]);

javascript map

Shorthand: (key,value) Map 

const callbackMap = new Map<string, PushEventCallback>([
      ["addComment", addCommentCallback],
      ["commentModified", editCommentCallback]
]);

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#:~:text=Cloning%20and%20merging%20Maps

js map()

var number = [1, 2 , 3, 4, 5, 6, 7, 8, 9]; 
var doubles  = number.map((n) => { return n*2 })

/*  doubles 
    (9) [2, 4, 6, 8, 10, 12, 14, 16, 18] */

js Map

const result = new Map();//create a new map

result.set('a', 1);
result.set('b', 2);
console.log(result);

const germany = {name: 'Germany' , population: 8000000};//create a new object
result.set(germany, '80m');//set the object to the map

console.log(result);

result.delete('a');//delete the key 'a'
console.log(result);
result.clear();//clear all the keys in the map
console.log(result);

javascript map

const originals = [1, 2, 3];

const doubled = originals.map(item => item * 2);

console.log(doubled); // [2, 4, 6]

js map

const postIds = posts.map((post) => post.id);

array map

let numbers = [1, 2, 3, 4]
let filteredNumbers = numbers.map(function(num, index) {
  if (index < 3) {
     return num
  }
})
// index goes from 0, so the filterNumbers are 1,2,3 and undefined.
// filteredNumbers is [1, 2, 3, undefined]
// numbers is still [1, 2, 3, 4]

javascript array map

const array = [1, 4, 9, 16];

const arrayWithMultipliedElems = array.map(elem => elem * 2);

console.log(arrayWithMultipliedElems); // [2, 8, 18, 32]

js array map

let A = [9000, 8500, 5500, 6500];
let B = A.map(function (value, index, array) {
    return value*2; // forEach 沒有在 return 的，所以不會有作用
});
console.log(B); // undefined

Array.map method

const shoppingList = ['Oranges', 'Cassava', 'Garri', 'Ewa', 'Dodo', 'Books']

export default function List() {
  return (
    <>
      {shoppingList.map((item, index) => {
        return (
          <ol>
            <li key={index}>{item}</li>
          </ol>
        )
      })}
    </>
  )
}