JAVASCRIPT

How does map works in javascript?

const products = [
    { name: 'Laptop', price: 32000, brand: 'Lenovo', color: 'Silver' },
    { name: 'Phone', price: 700, brand: 'Iphone', color: 'Golden' },
    { name: 'Watch', price: 3000, brand: 'Casio', color: 'Yellow' },
    { name: 'Aunglass', price: 300, brand: 'Ribon', color: 'Blue' },
    { name: 'Camera', price: 9000, brand: 'Lenovo', color: 'Gray' },
];

const productName = products.map(product => product.name);
console.log(productName);
//Expected output:[ 'Laptop', 'Phone', 'Watch', 'Aunglass', 'Camera' ]

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);

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];

how to use the map method in javascript

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

const bigNumbers = numbers.map(number => {
  return number * 10;
});

how the map function works javascript

const array = [2, 5, 9];
let squares = array.map((num) => num * num);

console.log(array); // [2, 5, 9]
console.log(squares); // [4, 25, 81]

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]

map in javascript

// Use map to create a new array in memory. Don't use if you're not returning
const arr = [1,2,3,4]

// Get squares of each element
const sqrs = arr.map((num) => num ** 2)
console.log(sqrs)
// [ 1, 4, 9, 16 ]

//Original array untouched
console.log(arr)
// [ 1, 2, 3, 4 ]

map method js

// Map objects are collections of key-value pairs. 
// A key in the Map may only occur once, it is unique in the Map 's collection
let map = new Map()
let keyArray = 'Array'
map.set(keyArray, [1, 2, 3, 4, 5])
map.get(keyArray) // 1, 2, 3, 4, 5

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);

map in js

//map() methods returns a new array
const data = {name: "laptop", brands: ["dell", "acer", "asus"]}
let inside_data = data.brands.map((i) => {
	console.log(i); //dell acer asus
});

map in javascript

//map is higher order function 
const names= ["Shirshak","SabTech","Fiverr"]
const newNames= names.map(function(name){
 console.log(video)
})
console.log(newVideos) //(3) [undefined, undefined, undefined]
//map always try to return somethings if we don't return we get undefined.

//map is used for modification,copy of array.
//copy of array using map
const newNames= names.map(function(name){
return name;
})

map js

const arr = [1,2,3,4,5]

const modifiedArr = arr.map((val) => {    // takes callback and returns modified array
	return val * 5
})
// map doesn't modify original array!
// arr = [1,2,3,4,5]
// modifiedArr = [5,10,15,20,25]

map in javascript

const arr = [1, 2, 3, 4, 5, 6];
const mapped = arr.map(el => el + 20);	//[21, 22, 23, 24, 25, 26]

javascript map

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

JavaScript Array map()

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

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

map in javascript

['elem', 'another', 'name'].map((value, index, originalArray) => { 
  console.log(.....)
});

map in javascript

let myMap = new Map()

let keyString = 'a string'
let keyObj    = {}
// setting the values
myMap.set(keyString, "value associated with 'a string'")
myMap.set(keyObj, 'value associated with keyObj')
myMap.set(keyFunc, 'value associated with keyFunc')
myMap.size              // 3
// getting the values
myMap.get(keyString)    // "value associated with 'a string'"
myMap.get(keyObj)       // "value associated with keyObj"
myMap.get(keyFunc)      // "value associated with keyFunc"

map javascript

var miMapa = new Map();

var claveObj = {},
    claveFunc = function () {},
    claveCadena = "una cadena";

// asignando valores
miMapa.set(claveCadena, "valor asociado con 'una cadena'");
miMapa.set(claveObj, "valor asociado con claveObj");
miMapa.set(claveFunc, "valor asociado with claveFunc");

miMapa.size; // 3

// obteniendo los valores
miMapa.get(claveCadena);    // "valor asociado con 'una cadena'"
miMapa.get(claveObj);       // "valor asociado con claveObj"
miMapa.get(claveFunc);      // "valor asociado con claveFunc"

miMapa.get("una cadena");   // ""valor asociado con 'una cadena'"
                         // porque claveCadena === 'una cadena'
miMapa.get({});           // undefined, porque claveObj !== {}
miMapa.get(function() {}) // undefined, porque claveFunc !== function () {}

var myMap = new Map();
myMap.set("bar", "foo");

myMap.delete("bar"); // Retorna true. Eliminado con éxito.
myMap.has("bar");    // Retorna false. El elemento "bar" ya no está presente.

map javascript

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

map function in js

var array = "M 175 0 L 326.55444566227675 87.50000000000001 L 326.55444566227675 262.5 L 175 350 L 23.445554337723223 262.5 L 23.44555433772325 87.49999999999999 L 175 0".split(" ");

let neWd = array.map(x => {
	if (x === 'M' || x === 'L'){
		return x;
	}else{
		return x * 2;
	}
}).join(' ')

console.log(neWd);

map javascript

test.map(x=> x)

map javascript

var kvArray = [["clave1", "valor1"], ["clave2", "valor2"]];

// El constructor por defecto de Map para transforar un Array 2D (clave-valor) en un mapa
var miMapa = new Map(kvArray);

miMapa.get("clave1"); // devuelve "valor1"

// Usando la función Array.from para transformar el mapa a un Array 2D clave-valor.
console.log(Array.from(miMapa)); // Muestra exactamente el mismo Array que kvArray

// O usando los iteradores de claves o valores y convirtiendo a array.
console.log(Array.from(miMapa.keys())); // Muestra ["clave1", "clave2"]

map values js

function mapValues(value, oldRange, newRange) {
    var newValue = (value - oldRange[0]) * (newRange[1] - newRange[0]) / (oldRange[1] - oldRange[0]) + newRange[0];
    return Math.min(Math.max(newValue, newRange[0]) , newRange[1]);
}

javascript map

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

JavaScript map method

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)

JavaScript Map Function

const myAwesomeArray = [5, 4, 3, 2, 1]

myAwesomeArray.map(x => x * x)

// >>>>>>>>>>>>>>>>> Output: [25, 16, 9, 4, 1]

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

map javascript

//forEach vs. Map High Order Array Methods
const arr = [1,2,3]
const arr2 = [...arr,4,5]//see spread operator grepper answer for [...arr]
//the forEach doesn't return anything, it just loops through the array
arr2.forEach(function(item) {
  console.log(item + ' of ' + arr2.length)
})
//map allows us to return an array and store it into a new array
const arr3 = arr2.map(function(item) {
  //after performing some operation on all the objects of the array
  //we can then return all those values into a new array
  return item * 2
})

console.log(arr3)

map javascript

// use the map method on an array.

// define array
let scores = [10, 25, 30]

// use of map, we store the map method in to a variable called doubledScore
let doubledScore = scores.map(function(score) {
	return score * 2 // returns every value of the array * 2 
})


console.log(doubledScore) // [20, 50, 60]

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);

map function

# map function
city_lengths = map(len, ['sanjose', 'cupertino', 'sunnyvale', 'fremont'])
print(list(city_lengths))

# [7, 9, 9, 7]
# Map takes a function and a collection of items. It makes a new, empty collection, runs the function on each item in the original collection and inserts each return value into the new collection. It returns the new collection.

map function javascript

var rebels = pilots.filter(function (pilot) {  return pilot.faction === "Rebels";});var empire = pilots.filter(function (pilot) {  return pilot.faction === "Empire";});

map function

const ratings = watchList.map(item => ({
  title: item["Title"],
  rating: item["imdbRating"]
}));

map method in javascript

const colorData = ['red','blue','green']
const result = colorData.map((el)=>el)
console.log(result)

javascript array map

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

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

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

function with .map javascript

const numbers = [2, 7, 9, 171, 52, 33, 14]
const toSquare = num => num * num

const squareNums = newNumbers => 
  newNumbers.map(toSquare);

console.log(squareNums(numbers));

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

How does map works in javascript?

const products = [
    { name: 'Laptop', price: 32000, brand: 'Lenovo', color: 'Silver' },
    { name: 'Phone', price: 700, brand: 'Iphone', color: 'Golden' },
    { name: 'Watch', price: 3000, brand: 'Casio', color: 'Yellow' },
    { name: 'Aunglass', price: 300, brand: 'Ribon', color: 'Blue' },
    { name: 'Camera', price: 9000, brand: 'Lenovo', color: 'Gray' },
];

const productName = products.map(product => product.name);
console.log(productName);
//Expected output:[ 'Laptop', 'Phone', 'Watch', 'Aunglass', 'Camera' ]

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);

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];

how to use the map method in javascript

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

const bigNumbers = numbers.map(number => {
  return number * 10;
});

how the map function works javascript

const array = [2, 5, 9];
let squares = array.map((num) => num * num);

console.log(array); // [2, 5, 9]
console.log(squares); // [4, 25, 81]

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]

map in javascript

// Use map to create a new array in memory. Don't use if you're not returning
const arr = [1,2,3,4]

// Get squares of each element
const sqrs = arr.map((num) => num ** 2)
console.log(sqrs)
// [ 1, 4, 9, 16 ]

//Original array untouched
console.log(arr)
// [ 1, 2, 3, 4 ]

map method js

// Map objects are collections of key-value pairs. 
// A key in the Map may only occur once, it is unique in the Map 's collection
let map = new Map()
let keyArray = 'Array'
map.set(keyArray, [1, 2, 3, 4, 5])
map.get(keyArray) // 1, 2, 3, 4, 5

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);

map in js

//map() methods returns a new array
const data = {name: "laptop", brands: ["dell", "acer", "asus"]}
let inside_data = data.brands.map((i) => {
	console.log(i); //dell acer asus
});

map in javascript

//map is higher order function 
const names= ["Shirshak","SabTech","Fiverr"]
const newNames= names.map(function(name){
 console.log(video)
})
console.log(newVideos) //(3) [undefined, undefined, undefined]
//map always try to return somethings if we don't return we get undefined.

//map is used for modification,copy of array.
//copy of array using map
const newNames= names.map(function(name){
return name;
})

map js

const arr = [1,2,3,4,5]

const modifiedArr = arr.map((val) => {    // takes callback and returns modified array
	return val * 5
})
// map doesn't modify original array!
// arr = [1,2,3,4,5]
// modifiedArr = [5,10,15,20,25]

map in javascript

const arr = [1, 2, 3, 4, 5, 6];
const mapped = arr.map(el => el + 20);	//[21, 22, 23, 24, 25, 26]

javascript map

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

JavaScript Array map()

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

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

map in javascript

['elem', 'another', 'name'].map((value, index, originalArray) => { 
  console.log(.....)
});

map in javascript

let myMap = new Map()

let keyString = 'a string'
let keyObj    = {}
// setting the values
myMap.set(keyString, "value associated with 'a string'")
myMap.set(keyObj, 'value associated with keyObj')
myMap.set(keyFunc, 'value associated with keyFunc')
myMap.size              // 3
// getting the values
myMap.get(keyString)    // "value associated with 'a string'"
myMap.get(keyObj)       // "value associated with keyObj"
myMap.get(keyFunc)      // "value associated with keyFunc"

map javascript

var miMapa = new Map();

var claveObj = {},
    claveFunc = function () {},
    claveCadena = "una cadena";

// asignando valores
miMapa.set(claveCadena, "valor asociado con 'una cadena'");
miMapa.set(claveObj, "valor asociado con claveObj");
miMapa.set(claveFunc, "valor asociado with claveFunc");

miMapa.size; // 3

// obteniendo los valores
miMapa.get(claveCadena);    // "valor asociado con 'una cadena'"
miMapa.get(claveObj);       // "valor asociado con claveObj"
miMapa.get(claveFunc);      // "valor asociado con claveFunc"

miMapa.get("una cadena");   // ""valor asociado con 'una cadena'"
                         // porque claveCadena === 'una cadena'
miMapa.get({});           // undefined, porque claveObj !== {}
miMapa.get(function() {}) // undefined, porque claveFunc !== function () {}

var myMap = new Map();
myMap.set("bar", "foo");

myMap.delete("bar"); // Retorna true. Eliminado con éxito.
myMap.has("bar");    // Retorna false. El elemento "bar" ya no está presente.

map javascript

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

map function in js

var array = "M 175 0 L 326.55444566227675 87.50000000000001 L 326.55444566227675 262.5 L 175 350 L 23.445554337723223 262.5 L 23.44555433772325 87.49999999999999 L 175 0".split(" ");

let neWd = array.map(x => {
	if (x === 'M' || x === 'L'){
		return x;
	}else{
		return x * 2;
	}
}).join(' ')

console.log(neWd);

map javascript

test.map(x=> x)

map javascript

var kvArray = [["clave1", "valor1"], ["clave2", "valor2"]];

// El constructor por defecto de Map para transforar un Array 2D (clave-valor) en un mapa
var miMapa = new Map(kvArray);

miMapa.get("clave1"); // devuelve "valor1"

// Usando la función Array.from para transformar el mapa a un Array 2D clave-valor.
console.log(Array.from(miMapa)); // Muestra exactamente el mismo Array que kvArray

// O usando los iteradores de claves o valores y convirtiendo a array.
console.log(Array.from(miMapa.keys())); // Muestra ["clave1", "clave2"]

map values js

function mapValues(value, oldRange, newRange) {
    var newValue = (value - oldRange[0]) * (newRange[1] - newRange[0]) / (oldRange[1] - oldRange[0]) + newRange[0];
    return Math.min(Math.max(newValue, newRange[0]) , newRange[1]);
}

javascript map

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

JavaScript map method

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)

JavaScript Map Function

const myAwesomeArray = [5, 4, 3, 2, 1]

myAwesomeArray.map(x => x * x)

// >>>>>>>>>>>>>>>>> Output: [25, 16, 9, 4, 1]

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

map javascript

//forEach vs. Map High Order Array Methods
const arr = [1,2,3]
const arr2 = [...arr,4,5]//see spread operator grepper answer for [...arr]
//the forEach doesn't return anything, it just loops through the array
arr2.forEach(function(item) {
  console.log(item + ' of ' + arr2.length)
})
//map allows us to return an array and store it into a new array
const arr3 = arr2.map(function(item) {
  //after performing some operation on all the objects of the array
  //we can then return all those values into a new array
  return item * 2
})

console.log(arr3)

map javascript

// use the map method on an array.

// define array
let scores = [10, 25, 30]

// use of map, we store the map method in to a variable called doubledScore
let doubledScore = scores.map(function(score) {
	return score * 2 // returns every value of the array * 2 
})


console.log(doubledScore) // [20, 50, 60]

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);

map function

# map function
city_lengths = map(len, ['sanjose', 'cupertino', 'sunnyvale', 'fremont'])
print(list(city_lengths))

# [7, 9, 9, 7]
# Map takes a function and a collection of items. It makes a new, empty collection, runs the function on each item in the original collection and inserts each return value into the new collection. It returns the new collection.

map function javascript

var rebels = pilots.filter(function (pilot) {  return pilot.faction === "Rebels";});var empire = pilots.filter(function (pilot) {  return pilot.faction === "Empire";});

map function

const ratings = watchList.map(item => ({
  title: item["Title"],
  rating: item["imdbRating"]
}));

map method in javascript

const colorData = ['red','blue','green']
const result = colorData.map((el)=>el)
console.log(result)

javascript array map

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

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

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

function with .map javascript

const numbers = [2, 7, 9, 171, 52, 33, 14]
const toSquare = num => num * num

const squareNums = newNumbers => 
  newNumbers.map(toSquare);

console.log(squareNums(numbers));

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