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Filter is the method of es6. Filter () is an array method added by es6 to filter array elements; this method passes array elements into a callback function to determine whether the element meets the specified condition, and returns with the syntax "arr.filter (callback function, thisValue)" if it does.

The operating environment of this tutorial: windows7 system, ECMAScript version 6, Dell G3 computer.

Filter () is a new array method added by es6 to filter array elements and return elements in the array that meet the specified criteria.

The filter () method passes the array element into a callback function, which determines whether the element meets the specified condition, and returns if it does.

Syntax:

Arr.filter (callback function, thisValue)

Callback function: this function is executed by every element in the array to specify conditions and process elements

ThisValue: optional. Object is used as the callback for this execution, passed to the function and used as the value of "this". If thisValue is omitted, the value of "this" is "undefined"

Format of the callback function:

Function callbackfn (Value,index,array)

Up to three parameters are acceptable:

Value: the value of the current array element, which cannot be omitted.

Index: the numeric index of the current array elements.

Array: the array object to which the current element belongs.

Return value: is a new array that contains a callback function that returns true for it. If the callback function returns false for all elements of array, the length of the new array is 0.

Example 1: returns all even numbers

Var a = [2 return false; 3 4 var 5 6 7 7 8]; function f (value) {if (value% 2 = = 0) {return true;} else {return false;}} var b = a.filter (f); console.log (b)

Output result:

Example 2: returns all leap years

Var a = [1995 return false; 1996 var b = a.filter (f); function f (value) {if (value%4==0 & & value0) {var b = a.filter (f);

Output result:

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