Zeega Style Guide

Based on idiomatic.js

Examples in JavaScript, but should be applied in other languages where applicable.

Table of Contents

• Whitespace
• Beautiful Syntax
• Type Checking (Courtesy jQuery Core Style Guidelines)
• Conditional Evaluation
• Practical Style
• Naming
• Misc
• Native & Host Objects
• Comments
• One Language Code

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1. Whitespace

• Use soft tabs (4 spaces)
• Use an empty before a return statement, unless it is the only line of a function
• Use an empty line after a variable declaration

2. Beautiful Syntax

   A. Parens, Braces, Linebreaks

   // 2.A.1.1
   // Use whitespace to promote readability
   
   if ( condition ) {
     // statements
   }
   
   if ( true ) {
     // statements
   } else {
     // statements
   }
   
   while ( condition ) {
     // statements
   }
   
   for ( var i = 0; i < 100; i++ ) {
     // statements
   }

   B. Assignments, Declarations, Functions ( Named, Expression, Constructor )

   // 2.B.1.1
   // Variables
   var foo = "bar",
     	num = 1,
     	undef;
   
   // Literal notations:
   var array = [],
     	object = {};
   
   // 2.B.1.2
   // Using only one `var` per scope (function) promotes readability
   // and keeps your declaration list free of clutter (also saves a few keystrokes)
   
   // Good
   var foo = "",
       bar = "",
     	quux;
   
   // 2.B.1.3
   // var statements should always be in the beginning of their respective scope (function).
   // Same goes for const and let from ECMAScript 6.
   
   function foo() {
   	var bar = "",
       	qux;
   
     	// all statements after the variables declarations.
   }

   // 2.B.2.1
   // Named Function Declaration
   function foo( arg1, argN ) {
   
   }
   
   // Usage
   foo( arg1, argN );
   
   // 2.B.2.3
   // Function Expression
   var square = function( number ) {
     	return number * number;
   };
   
   // 2.B.2.4
   // Constructor Declaration - Pascal Case
   function FooBar( options ) {
     	this.options = options;
   }
   
   // Usage
   var fooBar = new FooBar({ a: "alpha" });

   C. Exceptions, Slight Deviations

   // 2.C.1.1
   // Functions with callbacks
   foo(function() {
     	// Note there is no extra space between the first paren
     	// of the executing function call and the word "function"
   });
   
   // Function accepting an array, no space
   foo([ "alpha", "beta" ]);
   
   // 2.C.1.2
   // Function accepting an object, no space
   foo({
     a: "alpha",
     b: "beta"
   });
   
   // Single argument string literal, no space
   foo("bar");
   
   // Inner grouping parens, no space
   if ( !("foo" in obj) ) {
   
   }
   
   E. Quotes

    Always use single quotes
   

   F. End of Lines and Empty Lines
   
   Whitespace can ruin diffs and make changesets impossible to read. Consider incorporating a pre-commit hook that removes end-of-line whitespace and blanks spaces on empty lines automatically.
   
   

3. Type Checking (Courtesy jQuery Core Style Guidelines)

   A. Actual Types

   String:

    typeof variable === "string"
   

   Number:

    typeof variable === "number"
   

   Boolean:

    typeof variable === "boolean"
   

   Object:

    typeof variable === "object"
   

   Array:

    Array.isArray( arrayLikeObject )
    (wherever possible)
   

   Node:

    elem.nodeType === 1
   

   null:

    variable === null
   

   null or undefined:

    variable == null
   

   undefined:

   Global Variables:

    typeof variable === "undefined"
   

   Local Variables:

    variable === undefined
   

   Properties:

    object.prop === undefined
    object.hasOwnProperty( prop )
    "prop" in object
   

4. Conditional Evaluation

   // 4.1.1
   // When only evaluating that an array has length,
   // instead of this:
   if ( array.length > 0 ) ...
   
   // ...evaluate truthiness, like this:
   if ( array.length ) ...
   
   
   // 4.1.2
   // When only evaluating that an array is empty,
   // instead of this:
   if ( array.length === 0 ) ...
   
   // ...evaluate truthiness, like this:
   if ( !array.length ) ...
   
   
   // 4.1.3
   // When only evaluating that a string is not empty,
   // instead of this:
   if ( string !== "" ) ...
   
   // ...evaluate truthiness, like this:
   if ( string ) ...
   
   
   // 4.1.4
   // When only evaluating that a string _is_ empty,
   // instead of this:
   if ( string === "" ) ...
   
   // ...evaluate falsy-ness, like this:
   if ( !string ) ...
   
   
   // 4.1.5
   // When only evaluating that a reference is true,
   // instead of this:
   if ( foo === true ) ...
   
   // ...evaluate like you mean it, take advantage of built in capabilities:
   if ( foo ) ...
   
   
   // 4.1.6
   // When evaluating that a reference is false,
   // instead of this:
   if ( foo === false ) ...
   
   // ...use negation to coerce a true evaluation
   if ( !foo ) ...
   
   // ...Be careful, this will also match: 0, "", null, undefined, NaN
   // If you _MUST_ test for a boolean false, then use
   if ( foo === false ) ...
   
   
   // 4.1.7
   // When only evaluating a ref that might be null or undefined, but NOT false, "" or 0,
   // instead of this:
   if ( foo === null || foo === undefined ) ...
   
   // ...take advantage of == type coercion, like this:
   if ( foo == null ) ...
   
   // Remember, using == will match a `null` to BOTH `null` and `undefined`
   // but not `false`, "" or 0
   null == undefined

5. Practical Style

   // 5.1.1
   // A Practical Module
   
   (function( global ) {
     var Module = (function() {
   
       var data = "secret";
   
       return {
         // This is some boolean property
         bool: true,
         // Some string value
         string: "a string",
         // An array property
         array: [ 1, 2, 3, 4 ],
         // An object property
         object: {
           lang: "en-Us"
         },
         getData: function() {
           // get the current value of `data`
           return data;
         },
         setData: function( value ) {
           // set the value of `data` and return it
           return ( data = value );
         }
       };
     })();
   
     // Other things might happen here
   
     // expose our module to the global object
     global.Module = Module;
   
   })( this );

   // 5.2.1
   // A Practical Constructor
   
   (function( global ) {
   
     function Ctor( foo ) {
   
       this.foo = foo;
   
       return this;
     }
   
     Ctor.prototype.getFoo = function() {
       return this.foo;
     };
   
     Ctor.prototype.setFoo = function( val ) {
       return ( this.foo = val );
     };
   
   
     // To call constructor's without `new`, you might do this:
     var ctor = function( foo ) {
       return new Ctor( foo );
     };
   
   
     // expose our constructor to the global object
     global.ctor = ctor;
   
   })( this );

6. Naming

   // 6.A.3.1
   // Naming strings
   
   `dog` is a string
   
   
   // 6.A.3.2
   // Naming arrays
   
   `dogs` is an array of `dog` strings
   
   
   // 6.A.3.3
   // Naming functions, objects, instances, etc
   
   camelCase; function and var declarations
   
   
   // 6.A.3.4
   // Naming constructors, prototypes, etc.
   
   PascalCase; constructor function
   
   
   // 6.A.3.5
   // Naming regular expressions
   
   rDesc = //;
   
   
   // 6.A.3.6
   // From the Google Closure Library Style Guide
   
   functionNamesLikeThis;
   variableNamesLikeThis;
   ConstructorNamesLikeThis;
   EnumNamesLikeThis;
   methodNamesLikeThis;
   SYMBOLIC_CONSTANTS_LIKE_THIS;

   B. Faces of this

   Beyond the generally well known use cases of call and apply, always prefer .bind( this ) or a functional equivalent, for creating BoundFunction definitions for later invocation. Only resort to aliasing when no preferable option is available.

   // 6.B.1
   function Device( opts ) {
   
     this.value = null;
   
     // open an async stream,
     // this will be called continuously
     stream.read( opts.path, function( data ) {
   
       // Update this instance's current value
       // with the most recent value from the
       // data stream
       this.value = data;
   
     }.bind(this) );
   
     // Throttle the frequency of events emitted from
     // this Device instance
     setInterval(function() {
   
       // Emit a throttled event
       this.emit("event");
   
     }.bind(this), opts.freq || 100 );
   }
   
   // Just pretend we've inherited EventEmitter ;)

   When unavailable, functional equivalents to .bind exist in many modern JavaScript libraries.

   // 6.B.2
   
   // eg. lodash/underscore, _.bind()
   function Device( opts ) {
   
     this.value = null;
   
     stream.read( opts.path, _.bind(function( data ) {
   
       this.value = data;
   
     }, this) );
   
     setInterval(_.bind(function() {
   
       this.emit("event");
   
     }, this), opts.freq || 100 );
   }
   
   // eg. jQuery.proxy
   function Device( opts ) {
   
     this.value = null;
   
     stream.read( opts.path, jQuery.proxy(function( data ) {
   
       this.value = data;
   
     }, this) );
   
     setInterval( jQuery.proxy(function() {
   
       this.emit("event");
   
     }, this), opts.freq || 100 );
   }
   
   // eg. dojo.hitch
   function Device( opts ) {
   
     this.value = null;
   
     stream.read( opts.path, dojo.hitch( this, function( data ) {
   
       this.value = data;
   
     }) );
   
     setInterval( dojo.hitch( this, function() {
   
       this.emit("event");
   
     }), opts.freq || 100 );
   }

   As a last resort, create an alias to this using self as an Identifier. This is extremely bug prone and should be avoided whenever possible.

   // 6.B.3
   
   function Device( opts ) {
     var self = this;
   
     this.value = null;
   
     stream.read( opts.path, function( data ) {
   
       self.value = data;
   
     });
   
     setInterval(function() {
   
       self.emit("event");
   
     }, opts.freq || 100 );
   }

   C. Use thisArg

   Several prototype methods of ES 5.1 built-ins come with a special thisArg signature, which should be used whenever possible

   // 6.C.1
   
   var obj;
   
   obj = { f: "foo", b: "bar", q: "qux" };
   
   Object.keys( obj ).forEach(function( key ) {
   
     // |this| now refers to `obj`
   
     console.log( this[ key ] );
   
   }, obj ); // <-- the last arg is `thisArg`
   
   // Prints...
   
   // "foo"
   // "bar"
   // "qux"

   thisArg can be used with Array.prototype.every, Array.prototype.forEach, Array.prototype.some, Array.prototype.map, Array.prototype.filter

7. Misc

   This section will serve to illustrate ideas and concepts that should not be considered dogma, but instead exists to encourage questioning practices in an attempt to find better ways to do common JavaScript programming tasks.

   A. Using switch should be avoided, modern method tracing will blacklist functions with switch statements

   There seems to be drastic improvements to the execution of switch statements in latest releases of Firefox and Chrome. http://jsperf.com/switch-vs-object-literal-vs-module

   Notable improvements can be witnesses here as well: rwaldron/idiomatic.js#13

   // 7.A.1.1
   // An example switch statement
   
   switch( foo ) {
     case "alpha":
       alpha();
       break;
     case "beta":
       beta();
       break;
     default:
       // something to default to
       break;
   }
   
   // 7.A.1.2
   // A alternate approach that supports composability and reusability is to
   // use an object to store "cases" and a function to delegate:
   
   var cases, delegator;
   
   // Example returns for illustration only.
   cases = {
     alpha: function() {
       // statements
       // a return
       return [ "Alpha", arguments.length ];
     },
     beta: function() {
       // statements
       // a return
       return [ "Beta", arguments.length ];
     },
     _default: function() {
       // statements
       // a return
       return [ "Default", arguments.length ];
     }
   };
   
   delegator = function() {
     var args, key, delegate;
   
     // Transform arguments list into an array
     args = [].slice.call( arguments );
   
     // shift the case key from the arguments
     key = args.shift();
   
     // Assign the default case handler
     delegate = cases._default;
   
     // Derive the method to delegate operation to
     if ( cases.hasOwnProperty( key ) ) {
       delegate = cases[ key ];
     }
   
     // The scope arg could be set to something specific,
     // in this case, |null| will suffice
     return delegate.apply( null, args );
   };
   
   // 7.A.1.3
   // Put the API in 7.A.1.2 to work:
   
   delegator( "alpha", 1, 2, 3, 4, 5 );
   // [ "Alpha", 5 ]
   
   // Of course, the `case` key argument could easily be based
   // on some other arbitrary condition.
   
   var caseKey, someUserInput;
   
   // Possibly some kind of form input?
   someUserInput = 9;
   
   if ( someUserInput > 10 ) {
     caseKey = "alpha";
   } else {
     caseKey = "beta";
   }
   
   // or...
   
   caseKey = someUserInput > 10 ? "alpha" : "beta";
   
   // And then...
   
   delegator( caseKey, someUserInput );
   // [ "Beta", 1 ]
   
   // And of course...
   
   delegator();
   // [ "Default", 0 ]
   

   B. Early returns promote code readability with negligible performance difference

   // 7.B.1.1
   // Bad:
   function returnLate( foo ) {
     var ret;
   
     if ( foo ) {
       ret = "foo";
     } else {
       ret = "quux";
     }
     return ret;
   }
   
   // Good:
   
   function returnEarly( foo ) {
   
     if ( foo ) {
       return "foo";
     }
     return "quux";
   }

8. Comments

   Single line above the code that is subject

   Multiline is good

   End of line comments are prohibited!

   JSDoc style is good, but requires a significant time investment

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Principles of Writing Consistent, Idiomatic JavaScript by Rick Waldron and Contributors is licensed under a Creative Commons Attribution 3.0 Unported License.
Based on a work at github.com/rwldrn/idiomatic.js.