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This article mainly introduces "whether the variable of javascript needs to be declared". In the daily operation, I believe that many people have doubts about whether the variable of javascript needs to be declared. The editor consulted all kinds of data and sorted out a simple and easy-to-use method of operation. I hope it will be helpful to answer the doubt of "whether the variable of javascript needs to be declared". Next, please follow the editor to study!

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

The variable is equivalent to the container, the value is equivalent to what is contained in the container, and the variable name is the label affixed to the container, through which you can find the variable so that you can read and write the value it stores.

Does the javascript variable need to be declared?

In strict mode, variables must be declared before they can be used.

In non-strict mode, JavaScript allows you to assign values to variables without declaring them, because the JavaScript interpreter can automatically implicitly declare variables. Implicitly declared variables are always used as global variables.

Declare variable

In JavaScript, var statements are used to declare variables.

Example 1

In a var statement, one or more variables can be declared or assigned, and unassigned variables are initialized to undefined (undefined) values. When declaring multiple variables, you should use comma operators to separate them.

Var a; / declare a variable var a clean bjournal; / / declare multiple variables var b = 1; / / declare and assign [xss_clean] (a); / / return undefined [XSS _ clean] (b); / / return 1

Example 2

In JavaScript, you can declare the same variable repeatedly, or you can initialize the value of the variable repeatedly.

Var a = 1 position var a = 2 10 var a = 3; [xss_clean] (a); / / return 3 to this point, the study on "whether the variable of javascript needs to be declared" is over, hoping to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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