How to use forEach(), Array.map() and Array.filter()? (code example)

This article will introduce to you the usage of forEach(), Array.map() and Array.filter(). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

Array.forEach()

The forEach() method calls the function once for each array element (Callback). [Related course recommendations:JavaScript video tutorial]

     
JavaScript Array.forEach()
 
为每个数组元素调用一次函数。
 
   

Please note that this function has 3 parameters:

● Element value

● Element index

●The array itself

The above example only uses the value parameter. The example can be rewritten as:

     
JavaScript Array.forEach()
 
为每个数组元素调用一次函数。
 
   

Array.map()

The map() method works by executing a function on each array element. Create new array. The map() method is a function that does not execute array elements without values. The map() method does not change the original array.

This example multiplies each array value by 2:

     
JavaScript Array.map()
 
通过对每个数组元素执行函数来创建新数组。
 
   

Please note that this function has 3 parameters:

● Element value

● Element index

●The array itself

When the callback function only uses the value parameter, the index and array parameters can be omitted:

   
JavaScript Array.map()
 
通过对每个数组元素执行函数来创建新数组。
 
   

Array.filter( )

#filter() method creates a new array containing the array elements of the passed test. This example creates a new array from elements with values greater than 18:

     
JavaScript Array.filter()
 
使用通过测试的所有数组元素创建一个新数组。
 
   

Note that this function has 3 parameters:

● Element value

● Element index

●The array itself

     
JavaScript Array.filter()
 
使用通过测试的所有数组元素创建一个新数组。
 
   

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