includes() vs indexOf() in JS, let’s talk about their differences

This article will briefly compare the includes() and indexOf() methods in JavaScript and talk about their differences. I hope it will be helpful to you!

1. Basic difference

• ##includes() and indexOf() They are all used to check whether the array contains certain elements. The return value of includes() is a Boolean value, and indexOf() returns the index value. If not, it returns

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let arr = [1,2,3]
arr.indexOf(0)	// -1
arr.indexOf(2)	// 1
arr.includes(2)	// true

2. Check NAN and undefined

• Because indexOf() strictly follows the === operator to compare values, indexOf() cannot check NAN, but includes() can

let arr = [NaN,]
arr.indexOf(NaN)	// -1
arr.indexOf(undefined) // -1
arr.includes(NaN)	// true
arr.includes(undefined)	// true

3. Check -0 and 0

• includes() and indexOf() do not distinguish between -0 and 0. When judging, Thinking that the two are the same

let arr = [+0]
arr.includes(-0) // true
arr.indexOf(-0) // 0

4. Complex data types cannot be checked

• Both can only judge simple data types, but cannot judge complex data types such as objects and arrays

let arr = [{a:1},{a:2}]
arr.includes({a:1}) // false
arr.indexOf({a:1}) // -1

5. indexOf() can be used for strings

• Returns the position where the specified character appears for the first time, and there is an implicit conversion

let str = 'a1b2c3'
str.indexOf('2')); //3
str.indexOf(1)); //3

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