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This article will explain in detail how to use the keyword var to declare variables in es6. The editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

Declare variables with the keyword var

Var a; / / undefinedvar b = 1

Variables defined by var can be modified. If not initialized, undefined will be output and no error will be reported.

The variable declared by var is on window. Use let or const to declare the variable. This variable will not be placed on window.

There are block-level scopes in many languages, but JS does not. It uses var to declare variables and demarcates scopes by function. Curly braces "{}" do not limit the scope of var, so variables declared with var have the effect of variable promotion.

The variable scope declared by var is global or functional

This is the end of this article on "how to declare variables with the keyword var in es6". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it out for more people to see.

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