Style Guide

This page outlines the style conventions that PDF.js follows to maintain a consistent codebase. We ask each contributor that creates a pull request to adhere to these conventions.
Many of these conventions will also be checked automatically by a linting tool after each push to a branch of a pull request. Please refer to https://github.com/mozilla/pdf.js/wiki/Contributing#4-run-lint-and-testing for information about running the linting tool locally.

General

• Indentation: 2 spaces
• Line length: 80 characters
• Required license in header: see https://github.com/mozilla/pdf.js/blob/master/src/license_header.js

Naming

• Variables and functions: lowerCamelCase
• Constructor-like functions: UpperCamelCase
• Constants: ALL_UPPER_CASE_WITH_UNDERSCORES

Braces

Always use braces and put them on same line, even for single line control statements:

if (someVar) {
  return true;
} else {
  return null;
}

White space

Keep one space after control statements (if, else, while, for, et cetera):

if (someVar) {

Equalities

Use only strict equalities (===) and inequalities (!==):

if (someVar === conditionA) {
  return true;
} else if (someVar !== conditionB) {
  return false;
}

Variables

Variables must be defined only once within a function scope, preferably at the top of the function.

Classes

The standard way of creating classes in PDF.js, when adding new code, is the following. Please note that by class we mean an object that is class-like.

var ClassName = (function ClassNameClosure() {
  function ClassName(...) {
    ...
  }

  ClassName.prototype = {
    functionName(arg1, arg2, ...) {
      ...
    },

    anVeryVeryVeryLongFunctionName(arg1,
                                   arg2,
                                   ...) {
      ...
    },
  };

  return ClassName;
})();