Variables can hold different types of values at different times : Variables « Language Basics « JavaScript Tutorial

A variable can be initialized with a string value, and later on be set to a number value.

var test = "hi";
alert(test);
test = 55;
alert(test);

1.9.Variables
	1.9.1.	Variables
	1.9.2.	Variables can hold different types of values at different times
	1.9.3.	Naming Variables
	1.9.4.	Variables don't have to be declared before being used
	1.9.5.	Define variable and assign value
	1.9.6.	Reassigning value to Variables
	1.9.7.	Working With JavaScript Variables
	1.9.8.	Declare two variables in the same line
	1.9.9.	Reference a variable without declaration
	1.9.10.	Assign one variable to another variable
	1.9.11.	Do simple calculation
	1.9.12.	Braces indicate code blocks