Question

When you want a JavaScript file (or function) to be parsed in “strict mode” you can put..

"use strict";

..in the top of your JavaScript file (or function).

This “use strict”; is a so-called “pragma”.

My question: what exactly is a pragma?
The closest thing I can think of is a “directive”.

Answer 1

compiler directives are called pragmas (short for “pragmatic information”).

http://en.wikipedia.org/wiki/Preprocessor_directive

It’s a pre-processor directive, or like code metadata. It’s similar to other languages or compilers that use stuff like this more. It’s pragmatic information about how to interpret the code that follows.

And as far as I know, this is the only one in JavaScript. It’s sort of a hack to force modern interpreters to behave in a certain way, but without breaking older interpreters.