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typedArray.reduceRight

The reduceRight() method applies a function against an accumulator and each value of the typed array (from right-to-left) has to reduce it to a single value. This method has the same algorithm as Array.prototype.reduceRight(). TypedArray is one of the typed array types here.

Syntax

typedarray.reduceRight(callback[, initialValue])

Parameters

callback
Function to execute on each value in the typed array, taking four arguments:
previousValue
The value previously returned in the last invocation of the callback, or initialValue, if supplied (see below).
currentValue
The current element being processed in the typed array.
index
The index of the current element being processed in the typed array.
array
The typed array reduce was called upon.
initialValue
Optional. Object to use as the first argument to the first call of the callback.

Return value

The value that results from the reduction.

Description

The reduceRight method executes the callback function once for each element present in the typed array, excluding holes in the typed array, receiving four arguments: the initial value (or value from the previous callback call), the value of the current element, the current index, and the typed array over which iteration is occurring.

The call to the reduceRight callback would look something like this:

typedarray.reduceRight(function(previousValue, currentValue, index, typedarray) {
  // ...
});

The first time the function is called, the previousValue and currentValue can be one of two values. If an initialValue was provided in the call to reduceRight, then previousValue will be equal to initialValue and currentValue will be equal to the last value in the typed array. If no initialValue was provided, then previousValue will be equal to the last value in the typed array and currentValue will be equal to the second-to-last value.

If the typed array is empty and no initialValue was provided, TypeError would be thrown. If the typed array has only one element (regardless of position) and no initialValue was provided, or if initialValue is provided but the typed array is empty, the solo value would be returned without calling callback.

Examples

Sum up all values within an array

var total = new Uint8Array([0, 1, 2, 3]).reduceRight(function(a, b) {
  return a + b;
});
// total == 6

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
reduceRight 45 14 37 No 32 10
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
reduceRight 45 45 37 No 10 5.0
Server
Node.js
reduceRight 4.0.0

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/reduceRight