JavaScript Global Reference

The JavaScript global properties and functions can be used with all the built-in JavaScript objects.

JavaScript Global Properties

Property Description
Infinity A numeric value that represents positive/negative infinity
NaN The NaN property represents “Not-a-Number” value. This property indicates that a value is not a legal number.

The NaN property is the same as the Number.Nan property.

Tip: Use the isNaN() function to check if a value is a NaN value.

undefined Indicates that a variable has not been assigned a value

JavaScript Global Functions

Function Description
decodeURI() Decodes a URI
decodeURIComponent() Decodes a URI component
encodeURI() Encodes a URI
encodeURIComponent() Encodes a URI component
escape() Deprecated in version 1.5. Use encodeURI() or encodeURIComponent()instead
eval() Evaluates a string and executes it as if it was script code
isFinite() Determines whether a value is a finite, legal number
isNaN() Determines whether a value is an illegal number
Number() Converts an object’s value to a number
parseFloat() Parses a string and returns a floating point number
parseInt() Parses a string and returns an integer
String() Converts an object’s value to a string
unescape() Deprecated in version 1.5. Use decodeURI() or decodeURIComponent()instead

Functions or Methods?

It makes sense to call the list above global functions rather than global methods because the functions are called globally and not any objects.

Anyway, you can also call these functions methods, since they are methods of the global object where they run. In a web browser, the global object is the browser window. Then isNaN() is actually a window method: window.isNaN().