What does var in javascript mean?

var means "variable" and is a keyword in JavaScript. It is mainly used to declare variables. The syntax is "var variable name;"; after the variables are declared, if they are not assigned a value, then these variables will is assigned an initial value of "undefined".

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

var is a keyword in javascript, mainly used to declare variables. The syntax format is as follows:

var varname;

The var statement can declare one or more variables and optionally initialize them to a value; if multiple variables are defined, commas need to be used to separate the variable names. Open, as shown in the following example:

var varname1 [= value1] [, varname2 [= value2] ... [, varnameN [= valueN]]];

• varname: variable name. Variable names can be defined as any legal identifier.

• value: The initialization value of the variable. The value can be any legal expression. The default value is undefined.

After the variables are defined, if no values ​​are assigned to the variables, then these variables will be assigned an initial value - undefined (undefined).

After the variable is defined, you can use the equal sign = to assign a value to the variable. The left side of the equal sign is the name of the variable, and the right side of the equal sign is the value to be assigned to the variable, as shown in the following example:

var num;    // 定义一个变量 num
num = 1;    // 将变量 num 赋值为 1

In addition, you can also assign values ​​to variables while defining them, as shown in the following example:

var num = 1;                // 定义一个变量 num 并将其赋值为 1
var a = 2, b = 3, c = 4;    // 同时定义 a、b、c 三个变量并分别赋值为 2、3、4
// var a = 2,               // 为了让代码看起来更工整，上一行代码也可以写成这样
//     b = 3,
//     c = 4;

Extended information: Keyword

Keyword (Keyword) is JavaScript A set of names (or commands) used internally by a language. These names have specific uses. Users cannot customize identifiers with the same name. The specific instructions are shown in the table.

JavaScript Keywords

break	delete	if	this	while
case	do	in	throw	with
catch	else	instanceof	try
continue	finally	new	typeof
debugger（ECMAScript 5 new）	for	return	var
default	function	switch	void

[Recommended learning: javascript advanced tutorial】

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