JavaScript Array map()
Examples
Return a new array with the square root of all element values:
const numbers = [4, 9, 16, 25];
const newArr = numbers.map(Math.sqrt)
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Multiply all the values in an array with 10:
const numbers = [65, 44, 12, 4];
const newArr = numbers.map(myFunction)
function myFunction(num) {
return num * 10;
}
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More examples below.
Definition and Usage
map() creates a new array from calling a
function for every array element.
map() calls a function once for each element in an array.
map() does not execute the function for empty elements.
map() does not change the original array.
Syntax
array.map(function(currentValue, index, arr), thisValue)
Parameters
| Parameter | Description |
| function() | Required. A function to be run for each array element. |
| currentValue | Required. The value of the current element. |
| index | Optional. The index of the current element. |
| arr | Optional. The array of the current element. |
| thisValue | Optional. Default value undefined.A value passed to the function to be used as its this value. |
Return Value
| Type | Description |
| An array | The results of a function for each array element. |
More Examples
Get the full name for each person:
const persons = [
{firstname : "Malcom", lastname: "Reynolds"},
{firstname : "Kaylee", lastname: "Frye"},
{firstname : "Jayne", lastname: "Cobb"}
];
persons.map(getFullName);
function getFullName(item) {
return [item.firstname,item.lastname].join(" ");
}
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Browser Support
map() is an ECMAScript5 (ES5) feature.
ES5 (JavaScript 2009) fully supported in all browsers:
| Chrome | IE | Edge | Firefox | Safari | Opera |
| Yes | 9-11 | Yes | Yes | Yes | Yes |
