javascript.md

JavaScript

Naming

• Variable declarations should always be made using var to not declare them as global variables.

  Bad

  function sum(x, y) { result = x + y; return result; }

  Good

  function sum(x, y) { var result = x + y; return result; }

• use camelCase for variables and functions.

• Constants (like PI) are written in UPPERCASE.

• JavaScript files should have a .js extension.

• Constructors intended for use UpperCamelCase.

Syntax

• Always end a simple statement with a semicolon.

• In case of object use colon plus one space between each property and its value.

• In case of keys in object use quotes around string values, not around numeric values.

• Do not add a comma after the last property-value pair of an object.

• For understandability try to declare all variables at the top.

• To check both data type and values use '==='.

  Bad

  var a = "5"; var b = 5;

  if (a==b && typeof(a) == typeof(b)) { // do something }

  Good

  var a = "5"; var b = 5;

  if (a===b) { // do something
  }

Programming

• Use 2 space indentation.

• Always put spaces around operators ( = + - * / ), and after commas.

• Always put the opening brace on the same line as the previous statement.

  Bad

  function func() { return { "name": "Xyz" }; }

  Good

  function func () { return { "name": "Xyz" }; }

• whatever pattern you follow to place the braces, same pattern should be followed in all the places through-out the project

• The closing brace should be on the same indent as the original function call.

  Bad

  function func() { return { "name": "Xyz" }; }

  Good

  function func() { return { "name": "Xyz" }; }

• better to use if/else conditions over other ternary conditions though it is small.

• Don't use an empty line at the beginning or end of methods, blocks or conditionals. Use an empty line between methods, blocks and conditionals.

  bad

  if some_condition {

  // do something }

  good

  if some_condition { // do something }

  bad

  [2, 3, 4].map( function check(x) { return x*2; }) if some_condition { // do some thing }

  good

  [2, 3, 4].map( function check(x) { return x*2; })

  if some_condition { // do some thing }

• When a conditional is too long to fit on one line, successive lines must be indented one extra level to distinguish them from the body.

  bad

  if ( firstCondition() && secondCondition() && thirdCondition() ) { doStuff(); }

  good

  if ( firstCondition() && secondCondition() && thirdCondition() ) { doStuff(); }

• Switch cases are allowed to share the same code block. Example: switch (some_condition) { case 4: case 5: // do something break; }

• Javascript array can have data of different data types. Example: var a = [1,"a",2];