Javascript Basic Tutorial Variables_Basic Knowledge

Variables in JavaScript are declared using the var keyword (variable).

Copy code The code is as follows:

var school = "beijingyizhong"

You can also use the var keyword to give multiple values ​​to a variable.

Copy code The code is as follows:

var school = "beijingyizhong" , diqu = "beijing" , age = 100;

In addition, unlike java, javascript can store different data types in the same variable. For example

Copy code The code is as follows:

var school = "beijing";
document.write(school);
school = 132134;
document.write(school);

In addition, javascript can be used without declaring variables, for example:

Copy code The code is as follows:

var test1 = "i am teacher" ;
Test2 = test1 "PK yuan" ;
Document.write(test2);

When JavaScript encounters an undeclared variable, it will automatically create a global variable for it. For good usage habits, variables should be declared, which is good for work.

In addition, variable declaration should follow the following rules,

The first letter of a variable can be an uppercase or lowercase English letter, an underscore or the dollar "$" symbol
The remaining letters can be underscores, uppercase and lowercase letters, any numbers, or the dollar sign
The name of a variable cannot be a reserved word or keyword
Here are some legal variable names

Copy code The code is as follows:

var test;
var _beijing;
var $djas;

The following are some illegal variable names

Copy code The code is as follows:

var 4abcd; //Start with number
var asdf"dad; //Single quote is an illegal character
var false; // false is the keyword

The above is the entire content of this article. It is all very basic knowledge. I hope you will like it.