Join MDN and developers like you at Mozilla's View Source conference, 12-14 September in Berlin, Germany. Learn more at

Reserved syntax consisting of punctuation or alphanumeric characters that carrying out built-in functionality.  For example, in JavaScript the addition operator ("+") adds numbers together and concatenates strings, whereas the"not" operator ("!") negates an expression — for example making a true statement return false.

Learn more

General knowledge

Technical reference

Document Tags and Contributors

 Last updated by: chrisdavidmills,