const numbers1 = [45, 4, 9, 16, 25];
const numbers2 = numbers1.map(myFunction);
function myFunction(value, index, array) {
return value * 2;
}const numbers = [1, 2, 3, 4, 5];
const bigNumbers = numbers.map(number => {
return number * 10;
});let new_array = arr.map(function callback( currentValue[, index[, array]]) {
// return element for new_array
}[, thisArg])
function map(array, transform) {
let mapped = [];
for (let element of array) {
mapped.push(transform(element));
}
return mapped;
}
let rtlScripts = SCRIPTS.filter(s => s.direction == "rtl");
console.log(map(rtlScripts, s => s.name));
// → ["Adlam", "Arabic", "Imperial Aramaic", …]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]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