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Today, the editor will share with you the relevant knowledge points about the iterative method of JavaScript array, the content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

Array.map ()

The map () method creates a new array by executing a function on each array element.

The map () method does not perform functions on array elements that have no values.

The map () method does not change the original array.

This example multiplies each array value by 2:

Example

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

Var numbers2 = numbers1.map (myFunction)

Function myFunction (value, index, array) {

Return value * 2

}

Notice that the function takes three parameters:

Project value

Project index

The array itself

When the callback function only uses the value parameter, you can omit the index and array parameters:

Example

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

Var numbers2 = numbers1.map (myFunction)

Function myFunction (value) {

Return value * 2

}

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

Yes 9.0 Yes Yes Yes

Array.filter ()

The filter () method creates a new array containing elements of the array that pass the test.

This example creates a new array with elements with values greater than 18:

Example

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

Var over18 = numbers.filter (myFunction)

Function myFunction (value, index, array) {

Return value > 18

}

Note that this function accepts three parameters:

Project value

Project index

The array itself

In the above example, the callback function does not use index and array parameters, so you can omit them:

Example

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

Var over18 = numbers.filter (myFunction)

Function myFunction (value) {

Return value > 18

}

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

These are all the contents of the article "iterative methods of JavaScript arrays". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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