The difference between == and === in js

The difference between "==" and "===" in js: 1. "==" only judges the value but not the data type, while "===" judges the value and also the data type; 2. When using "==" for comparison, the data type can be automatically converted, but "===" cannot automatically convert the data type; 3. "===" is more rigorous, and it is recommended to use "===";

The operating system of this tutorial: windows10 system, JavaScript ECMAScript 2021 version, DELL G3 computer.

The difference between = = and === in js

= = and === are both used to determine equality , the difference is: equal degree of depth.

1.= = only judges the numerical value but not the data type. In other words, when using = = for comparison, it can automatically convert the data type for us;

2.=== determines the degree of equality deeper than ==, that is, it determines both the numerical value and the data type, and the data type cannot be automatically converted.

1, = = (the judgment values ​​are equal)

let a = 1; //数字类型
let b = ‘1’; //字符类型console.log(a==b);123

Result: true

2, === (congruent, judgment values ​​and types All equal)

let a = 1; //数字类型
let b = ‘1’;//字符类型
console.log(a===b);123

Result: false

Note: = = will automatically convert the data type, so sometimes some problems will occur, for example:

let a = 1;let b = true;console.log(a==b);//结果是true123
let a = 0;let b = false;console.log(a==b);//结果是true123
let a = null;let b = undefined;console.log(a==b);//结果是true123

Summary: === is more rigorous, it is recommended to use ===

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