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In this article Xiaobian for you to introduce in detail the "array iterative reduce and reduceRight method how to use", the content is detailed, the steps are clear, the details are handled properly, I hope that this "array iterative reduce and reduceRight method how to use" article can help you solve doubts, the following follow the editor's ideas slowly in-depth, together to learn new knowledge.

Array.reduce ()

The reduce () method runs the function on each array element to generate (decrease it) a single value.

The reduce () method works from left to right in the array. See also reduceRight ().

The reduce () method does not reduce the original array.

This example determines the sum of all the numbers in the array:

Example

Var numbers1 = [45, 4, 9, 16, 25]

Var sum = numbers1.reduce (myFunction)

Function myFunction (total, value, index, array) {

Return total + value

}

Note that this function accepts four parameters:

Total (initial value / previously returned value)

Project value

Project index

The array itself

The index and array parameters are not used in the above example. You can rewrite it as:

Example

Var numbers1 = [45, 4, 9, 16, 25]

Var sum = numbers1.reduce (myFunction)

Function myFunction (total, value) {

Return total + value

}

The reduce () method can accept an initial value:

Example

Var numbers1 = [45, 4, 9, 16, 25]

Var sum = numbers1.reduce (myFunction, 100)

Function myFunction (total, value) {

Return total + value

}

All browsers support Array.reduce (), except for Internet Explorer 8 or earlier:

Array.reduceRight ()

The reduceRight () method runs the function on each array element to generate (decrease it) a single value.

The reduceRight () method works from right to left in the array. See also reduce ().

The reduceRight () method does not reduce the original array.

This example determines the sum of all the numbers in the array:

Example

Var numbers1 = [45, 4, 9, 16, 25]

Var sum = numbers1.reduceRight (myFunction)

Function myFunction (total, value, index, array) {

Return total + value

}

Note that this function accepts four parameters:

Total (initial value / previously returned value)

Project value

Project index

The array itself

The index and array parameters are not used in the above example. You can rewrite it as:

Example

Var numbers1 = [45, 4, 9, 16, 25]

Var sum = numbers1.reduceRight (myFunction)

Function myFunction (total, value) {

Return total + value

}

All browsers support Array.reduceRight (), except for Internet Explorer 8 or earlier

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