The reduce()
method applies a function against an accumulator and each value of the typed array (from left-to-right) has to reduce it to a single value. This method has the same algorithm as Array.prototype.reduce()
. TypedArray is one of the typed array types here.
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Syntax
typedarray.reduce(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 reduce
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 first time the callback is called, previousValue
and currentValue
can be one of two values. If initialValue
is provided in the call to reduce
, then previousValue
will be equal to initialValue
and currentValue
will be equal to the first value in the typed array. If no initialValue
was provided, then previousValue
will be equal to the first value in the typed array and currentValue
will be equal to the second.
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
.
Polyfill
This method uses the same algorithm as Array.prototype.reduce()
, so the same polyfill can be used here: simply replace Array.prototype.reduce
with TypedArray.prototype.reduce
.
Examples
Sum up all values within an array
var total = new Uint8Array([0, 1, 2, 3]).reduce(function(a, b) { return a + b; }); // total == 6
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of '%TypedArray%.prototype.reduce' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
reduce | Chrome Full support 45 | Edge Full support 14 | Firefox Full support 37 | IE No support No | Opera Full support 32 | Safari Full support 10 | WebView Android Full support 45 | Chrome Android Full support 45 | Firefox Android Full support 37 | Opera Android No support No | Safari iOS Full support 10 | Samsung Internet Android Full support 5.0 | nodejs Full support 4.0.0 |
Legend
- Full support
- Full support
- No support
- No support