How to determine whether an element is in an array in es6

Judgment method: 1. Use "arr.includes(value)", if it returns true, it exists; 2. Use "arr.find(function(v){if(v==value{//true }})" statement; 3. Use "arr.some(i=>i===value)", if it returns true, it exists.

## The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

In es6, you can use the includes, find, and some methods to determine whether an element is in an array. Here is a detailed introduction.

Method 1: Use the includes method of es6

includes() method is used to determine whether an array contains a specified value and returns true or false. Syntax:

array.includes(searchElement, fromIndex);

• searchElement: the element to be found;

• fromIndex: the index position to start searching.

Example:

arr = [1,2,3,4,5]
console.log(arr.includes(5));

You can see that the return value is true, which means that element

5 is in the array.

Method 2 : Use the find method of es6

find() method returns the value of the first element of the array that passes the test (judged within the function).

find() method is in the array Each element of Call the execution function.

• If there is no element that meets the conditions, return undefined

• Example:

  var arr = [1,2,3,4,5]
  arr.find(function(value){
  	if(value==5){
  		console.log("指定元素在数组中");
  	}
  })

Method 3: Use the some method of es6

The some() method is used to detect whether there is an element that meets the specified conditions in the array. If it exists, it returns true, if it does not exist, it returns false.

arr = [1,2,3,4,5];
let istrue= arr.some(item => item === 45);
console.log(istrue);

You can see that the return value is false, which means the element is not in the array.

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