Introduction to JavaScript variables (with code)

This article brings you an introduction to JavaScript variables (with code). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Just like algebra, JavaScript variables are used to hold values ​​or expressions.

You can give the variable a short name, such as x, or a more descriptive name, such as length.

JavaScript variables can also hold text values, such as carname="Volvo".

Rules for JavaScript variable names:

• Variables are case-sensitive (y and Y are two different variables)
• Variables must start with a letter or an underscore

Note: Since JavaScript is case-sensitive, variable names are also case-sensitive.

Declare (Create) JavaScript Variables

Creating variables in JavaScript is often referred to as "declaring" variables.

You can declare JavaScript variables through the var statement:

var x;
var carname;

After the above declaration, the variables have no value, but you can assign values ​​to the variables while declaring them. :

var x=5;
var carname="Volvo";

Note: When assigning a text value to a variable, please enclose the value in quotes.

Assigning values ​​to JavaScript variables

Assigning values ​​to JavaScript variables through assignment statements:

x=5;
carname="Volvo";

The variable name is on the left side of the = symbol, and you need to assign to the variable The value of is to the right of =.

After the above statement is executed, the value saved in the variable x is 5, and the value of carname is Volvo .

Assigning a value to an undeclared JavaScript variable

If the variable you assign a value has not been declared, it will be automatically declared.

These statements:

x=5;
carname="Volvo";

Have the same effect as these statements:

var x=5;
var carname="Volvo";

Redeclare JavaScript variables

If you declare again JavaScript variable, the variable will not lose its original value.

var x=5;
var x;

After the above statement is executed, the value of variable x is still 5. The value of x is not reset or cleared when the variable is redeclared.

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