The sum of " + a + " and " + b + " plus " + c + " is " + ( a + b + c ); // Good var html = "

The sum of " + a + " and " + b + " plus " + c + " is " + ( a + b + c ); ``` Lines should be broken into logical groups if it improves readability, such as splitting each expression of a ternary operator onto its own line even if both will fit on a single line. ```js var baz = firstCondition( foo ) && secondCondition( bar ) ? qux( foo, bar ) : foo; ``` 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. ```js if ( firstCondition() && secondCondition() && thirdCondition() ) { doStuff(); } ``` ### Chained Method Calls When a chain of method calls is too long to fit on one line, there must be one call per line, with the first call on a separate line from the object the methods are called on. If the method changes the context, an extra level of indentation must be used. ```js elements .addClass( "foo" ) .children() .html( "hello" ) .end() .appendTo( "body" ); ``` ### Full File Closures When an entire file is wrapped in a closure, the body of the closure is not indented. ```js ( function( $ ) { // This doesn't get indented } )( jQuery ); ``` ```js module.exports = function( grunt ) { // This doesn't get indented }; ``` The same applies to AMD wrappers. ```js define( [ "foo", "bar", "baz" ], function( foo, bar, baz ) { // This doesn't get indented } ); ``` For UMD, the factory is indented to visually differentiate it from the body. ```js ( function( factory ) { if ( typeof define === "function" && define.amd ) { // AMD. Register as an anonymous module. define( [ "jquery" ], factory ); } else { // Browser globals factory( jQuery ); } }( function( $ ) { // This doesn't get indented } ) ); ``` ## Constructors Constructor functions should always be invoked with argument lists, even when such lists are empty. ```js throw new Error(); when = time || new Date(); ``` When property access or method invocation is immediately performed on the result of a constructor function, clarify precedence with wrapping parentheses. ```js detachedMode = ( new TemplateFactory( settings ) ).nodeType === 11; match = ( new RegExp( pattern ) ).exec( input ); ``` ## Equality Strict equality checks (`===`) must be used in favor of abstract equality checks (`==`). The _only_ exception is when checking for `undefined` and `null` by way of `null`. The use of `== null` is also acceptable in cases where only one of `null` or `undefined` may be logically encountered, such as uninitialized variables. ```js // Check for both undefined and null values, for some important reason. undefOrNull == null; ``` ## Type Checks - String: `typeof object === "string"` - Number: `typeof object === "number"` - Boolean: `typeof object === "boolean"` - Object: `typeof object === "object"` - Plain Object: `jQuery.isPlainObject( object )` - Function: `jQuery.isFunction( object )` - Array: `jQuery.isArray( object )` - Element: `object.nodeType` - null: `object === null` - null or undefined: `object == null` - undefined: - Global Variables: `typeof variable === "undefined"` - Local Variables: `variable === undefined` - Properties: `object.prop === undefined` ## Comments Comments are always preceded by a blank line. Comments start with a capital first letter, but don't require a period at the end, unless you're writing full sentences. There must be a single space between the comment token and the comment text. Single line comments go __over__ the line they refer to: ```js // We need an explicit "bar", because later in the code foo is checked. var foo = "bar"; // Even long comments that span // multiple lines use the single // line comment form. ``` Multi-line comments are only used for file and function headers. Inline comments are allowed as an exception when used to annotate special arguments in formal parameter lists or when needed to support a specific development tool: ```js function foo( types, selector, data, fn, /* INTERNAL */ one ) { // Do stuff } ``` Do not write API documentation in comments. API documentation lives in its own repository. ## Quotes jQuery uses double quotes. ```js var double = "I am wrapped in double quotes"; ``` Strings that require inner quoting must use double outside and single inside. ```js var html = "