A JavaScript variable is simply a name of storage location. There are two types of variables in JavaScript : local variable and global variable.
There are some rules while declaring a JavaScript variable (also known as identifiers).
- Name must start with a letter (a to z or A to Z), underscore( _ ), or dollar( $ ) sign.
- After first letter we can use digits (0 to 9), for example value1.
- JavaScript variables are case sensitive, for example x and X are different variables.
var x = 5;
var y = 6;
var z = x + y;
var y = 6;
var z = x + y;
From the example above, you can expect:
- x stores the value 5
- y stores the value 6
- z stores the value 11
JavaScript Identifiers
All JavaScript variables must be identified with unique names.
These unique names are called identifiers.
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
The general rules for constructing names for variables (unique identifiers) are:
- Names can contain letters, digits, underscores, and dollar signs.
- Names must begin with a letter
- Names can also begin with $ and _ (but we will not use it in this tutorial)
- Names are case sensitive (y and Y are different variables)
- Reserved words (like JavaScript keywords) cannot be used as names
JavaScript Data Types
JavaScript variables can hold numbers like 100 and text values like "John Doe".
In programming, text values are called text strings.
JavaScript can handle many types of data, but for now, just think of numbers and strings.
Strings are written inside double or single quotes. Numbers are written without quotes.
If you put a number in quotes, it will be treated as a text string.
var pi = 3.14;
var person = "John Doe";
var answer = 'Yes I am!';
var person = "John Doe";
var answer = 'Yes I am!';
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