Converting to a Number : Type Conversion « Number Data Type « JavaScript Tutorial

JavaScript has two methods for converting non-number primitives into numbers: parseInt() and parseFloat().

parseInt() converts a value into an integer.

parseFloat() converts a value into a floating-point number.

These methods only work properly when called on strings; all other types return NaN.

5.8.Type Conversion
	5.8.1.	Type Conversion
	5.8.2.	Type-conversion adheres to the following rules
	5.8.3.	Converting to a String
	5.8.4.	Using Number's toString() method in radix mode
	5.8.5.	Converting to a Number
	5.8.6.	parseInt() method
	5.8.7.	parseInt() in radix mode
	5.8.8.	If decimal numbers contain a leading zero, it's always best to specify the radix as 10 so that you won't accidentally end up with an octal value.
	5.8.9.	parseFloat() method
	5.8.10.	Type Casting
	5.8.11.	Casting to Boolean value
	5.8.12.	Casting to Number
	5.8.13.	Casting type to string
	5.8.14.	parseInt("33.00")
	5.8.15.	parseFloat("1.23e-2")
	5.8.16.	parseFloat("1.45inch")