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In this article Xiaobian for you to introduce in detail "JavaScript global variables and life cycle case analysis", the content is detailed, the steps are clear, the details are handled properly, I hope this "JavaScript global variables and life cycle case analysis" article can help you solve your doubts, following the editor's ideas slowly in depth, together to learn new knowledge.

JavaScript global variable

Variables are defined outside the function, that is, global variables.

Global variables have a global scope: all scripts and functions in a web page can be used.

Example

Var carName = "Volvo"

/ / the carName variable can be called here

Function myFunction () {

/ / the carName variable can be called within the function

}

If the variable is not declared within the function (without using the var keyword), it is a global variable.

In the following example, carName is within the function, but is a global variable.

Example

/ / the carName variable can be called here

Function myFunction () {

CarName = "Volvo"

/ / the carName variable can be called here

}

JavaScript variable life cycle

The JavaScript variable life cycle is initialized when it is declared.

The local variable is destroyed after the function has been executed.

Global variables are destroyed after the page is closed.

Function parameter

Function parameters only work within the function and are local variables.

Global variables in HTML

In HTML, global variables are window objects: all data variables belong to window objects.

Example

/ / you can use window.carName here

Function myFunction () {

CarName = "Volvo"

}

After reading this, the article "JavaScript Global variables and Lifecycle instance Analysis" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself to understand it. If you want to know more about related articles, you are welcome to follow the industry information channel.

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