/* 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];
// 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 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
// 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 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;
})
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"
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);
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"]
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 ͡°)
//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)
// 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]
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);