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This article introduces the knowledge of "how to reset variables in JavaScript". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Reset variable

Variables declared with the var keyword can be modified anywhere:

Case study

Var x = 2; / / legal

Var x = 3; / / legal

X = 4; / / legal

In the same scope or block-level scope, you cannot use the const keyword to reset variables declared by the var and let keywords:

Var x = 2; / / legal

Const x = 2; / / illegal

{

Let x = 2; / / legal

Const x = 2; / / illegal

}

You cannot use the const keyword to reset variables declared by the const keyword in the same scope or block-level scope:

Const x = 2; / / legal

Const x = 3; / / illegal

X = 3; / / illegal

Var x = 3; / / illegal

Let x = 3; / / illegal

{

Const x = 2; / / legal

Const x = 3; / / illegal

X = 3; / / illegal

Var x = 3; / / illegal

Let x = 3; / / illegal

}

The const keyword can redeclare assignments in different scopes or in different block-level scopes:

Const x = 2; / / legal

{

Const x = 3; / / legal

}

{

Const x = 4; / / legal

}

Variable lifting

Variables defined by the JavaScript var keyword can be declared after use, that is, variables can be used first and then declared (JavaScript variable promotion).

Case study

CarName = "Volvo"; / / you can use the carName variable here

Var carName

Variables defined by the const keyword cannot be declared after use, that is, variables need to be declared before they are used.

CarName = "Volvo"; / / you cannot use the carName variable here

Const carName = "Volvo"

That's all for "how to reset variables in JavaScript". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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