How to detect whether there is an element in an array in es6

Detection method: 1. Use the "arr.indexOf("element value")" statement, if the element index is returned, it exists; 2. Use "arr.includes("value")", if it exists, return true; 3. Use the for loop statement to traverse the array, and use the if statement and the "==" operator to determine whether the array element is the specified value.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

es6 Detect whether there is an element in the array

Method 1: array.indexOf

This method determines whether a certain value exists in the array. If it exists, it returns the subscript of the array element, otherwise it returns -1.

var arr=[1,2,3,4];
var index=arr.indexOf(3);
console.log(index);

Method 2: array.includes(searcElement[,fromIndex])

This method determines Whether there is a certain value in the array, if it exists, return true, otherwise return false

var arr=[1,2,3,4];
if(arr.includes(3))
    console.log("存在");
else
    console.log("不存在");

Method 3: Use for loop and if

var arr=[1,2,3,4];
var k=0;
for(var i=0;i<arr.length;i++){
    if(arr[i]==3)
        k=1;
}
if(k)
    console.log("存在");
else
    console.log("不存在");

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