What is the usage of '===' in javascript

"===" is a comparison operator built into JavaScript. It is used to determine whether a variable or value is absolutely equal in a logical statement, that is, the value and type are equal; the "===" operator will First compare whether the data types of the variables on both sides are equal, and then compare whether the values ​​​​of the variables on both sides are equal; only when the data types and values ​​​​are equal, true will be returned.

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

javascript === operator

"===" is a comparison operator built into JavaScript, used in logical statements. To determine whether variables or values ​​are equal; the return value is true or false.

"===" means identity, that is, absolute equality (both value and type are equal).

The "===" operator first compares whether the data types of the variables on both sides are equal, and then compares whether the values ​​​​of the variables on both sides are equal; only when the data types and values ​​​​are equal, the two variables are equal.

Example:

var x=5;
x==="5";  // 返回 false
x===5;   // 返回 true

[Recommended learning: javascript advanced tutorial】

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