JavaScript Array reduce()
Examples
Subtract all numbers in an array:
const numbers = [175, 50, 25];
document.getElementById("demo").innerHTML
= numbers.reduce(myFunc);
function myFunc(total, num) {
return total - num;
}
Try it Yourself »
Round all the numbers and display the sum:
const numbers = [15.5, 2.3, 1.1, 4.7];
document.getElementById("demo").innerHTML = numbers.reduce(getSum, 0);
function getSum(total, num) {
return total + Math.round(num);
}
Try it Yourself »
Definition and Usage
The reduce() method executes a reducer function for array element.
The reduce() method returns a single value: the function's accumulated result.
The reduce() method does not execute the function for empty array elements.
The reduce() method does not change the original array.
See Also:
Syntax
array.reduce(function(total, currentValue, currentIndex, arr), initialValue)
Parameters
| Parameter | Description | ||||||||
| function() | Required. A function to be run for each element in the array. |
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Reducer function parameters:
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| initialValue | Optional. A value to be passed to the function as the initial value. |
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Return Value
| The accumulated result from the last call of the callback function. |
Browser Support
reduce() 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 |
