Baseline Widely available
The reduce()
method of TypedArray
instances executes a user-supplied "reducer" callback function on each element of the typed array, in order, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements of the typed array is a single value. This method has the same algorithm as Array.prototype.reduce()
.
const uint8 = new Uint8Array([0, 1, 2, 3]);
function sum(accumulator, currentValue) {
return accumulator + currentValue;
}
console.log(uint8.reduce(sum));
// Expected output: 6
Syntax
reduce(callbackFn)
reduce(callbackFn, initialValue)
Parameters
callbackFn
A function to execute for each element in the typed array. Its return value becomes the value of the accumulator
parameter on the next invocation of callbackFn
. For the last invocation, the return value becomes the return value of reduce()
. The function is called with the following arguments:
accumulator
The value resulting from the previous call to callbackFn
. On the first call, its value is initialValue
if the latter is specified; otherwise its value is array[0]
.
currentValue
The value of the current element. On the first call, its value is array[0]
if initialValue
is specified; otherwise its value is array[1]
.
currentIndex
The index position of currentValue
in the typed array. On the first call, its value is 0
if initialValue
is specified, otherwise 1
.
array
The typed array reduce()
was called upon.
initialValue
Optional
A value to which accumulator
is initialized the first time the callback is called. If initialValue
is specified, callbackFn
starts executing with the first value in the typed array as currentValue
. If initialValue
is not specified, accumulator
is initialized to the first value in the typed array, and callbackFn
starts executing with the second value in the typed array as currentValue
. In this case, if the typed array is empty (so that there's no first value to return as accumulator
), an error is thrown.
The value that results from running the "reducer" callback function to completion over the entire typed array.
ExceptionsTypeError
Thrown if the typed array contains no elements and initialValue
is not provided.
See Array.prototype.reduce()
for more details. This method is not generic and can only be called on typed array instances.
const total = new Uint8Array([0, 1, 2, 3]).reduce((a, b) => a + b);
// total === 6
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