How to use filter function-JS Tutorial-php.cn

How to use filter function

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Release： 2019-02-21 16:08:33

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The arr.filter() function in How to use filter function is used to create a new array from a given array that contains only those elements in the given array that meet the conditions set by the parameter function. Let's take a closer look at how to use filter().

How to use filter function

The basic syntax of filter() is as follows:

var newArray = arr.filter(arg_function[, this_arg])

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The parameter of the filter() function is another function that defines each element of the array. Check the conditions. This arg_function itself has three parameters:

array: This is the array in which the .filter() function is called.

index: This is the index of the current element processed by the function.

element: This is the current element that the function is processing.

Another parameter this_arg is used to indicate that the function uses this value when executing the parameter function.

Let’s look at a specific example

The function filter() creates a new array that only contains elements that meet the conditions checked by the isPositive() function.

Example 1:

<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>

<script> 
function isPositive(value) { 
  return value > 0; 
} 
  
function func() { 
    var filtered = [112, 52, 0, -1, 944].filter(isPositive); 
    document.write(filtered); 
} 
func(); 
</script> 
</body>
</html>

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The output result is: 112,52,944

Example 2:

<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>
<script> 
function isEven(value) { 
  return value%2 == 0; 
} 
  
function func() { 
    var filtered = [11, 98, 31, 23, 944].filter(isEven); 
    document.write(filtered); 
} 
func(); 
</script> 
</body>
</html>

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The output result is: 98,944

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