js-rules.md

Rules

1. Syntax

1.1. Always use semicolons (;)

Bad:

    var a = 5
    var myFunction1 = function(){...}

Good:

    var myVar1 = 5;
    var myFunction1 = function(){...};

2. Naming

2.1. Use camel case names

Bad:

    var my-vovely_variable;
    var my-LovelyFunction = function(){...};
    var my-Lovely_obj = {
     dosometing:function(){...},
     "here-is-property":5
    }

Good:

    var myLovelyVariable;
    var myLovelyFunction = function(){};
    var myLovelyObj = {
     doSometing:function(){...},
     hereIsProperty:5
    };

2.2. Use NAMES_LIKE_THIS only for constant values.

Bad:

    example.settings.animationFps = 60;

Also Bad:

    example.settings.ANIMATION_FPS = currentNumberOfFrames/currentDelay;

Good:

    example.settings.ANIMATION_FPS = 60;

2.3. A function size must be less than 80 lines.

3. Code

3.1. Avoid using global variables

Bad:

    mySettings = {...};
    myOptions = {...};
    myProperties = {...};
    mySomething = {...};

Also Bad:

    window.mySettings = {...};
    window.myOptions = {...};
    window.myProperties = {...};
    window.mySomething = {...};

Good:

    window.XBS = {
      mySettings: {...},
      myOptions: {...},
      myProperties: {...},
      mySomething: {...}
    };

3.2. Declare with var

When you fail to specify var, the variable gets placed in the global context, potentially clobbering existing values. Also, if there's no declaration, it's hard to tell in what scope a variable lives (e.g., it could be in the Document or Window just as easily as in the local scope). So always declare with var.

Bad:

    myVar1 = 'Hello';
    myFunction1 = function(a){...};
    myFunction2(b){...};

Good:

    var myVar1 = 'Hello';
    var myFunction1 = function(a){...};
    var myFunction2 = function(b){...};

3.3. Declare variables in the begining of function declaration

Bad:

    var myFunction = function(){
    
      var myVar1 = 'Hello';
      myFunction2(myFunction1(myVar1));
      var myFunction1 = function(a){...};
      myFunction1(myVar1-myFunction2(33));
      var myFunction2(b){...};
      
    }

Good:

    var myFunction = function(){
    
      var myVar1 = 'Hello';
      var myFunction1 = function(a){...};
      var myFunction2(b){...};
      
      myFunction2(myFunction1(myVar1));
      myFunction1(myVar1-myFunction2(33));
      
    }

4. Dark forgotten powers

4.1 Do not use eval

Bad:

    var a = eval(json_text);

Good:

    var a = JSON.parse(json_text);

4.2 Do not use "with" command

Bad:

    var obj = { a: 123 };
    with(obj)
        alert(a);

Good:

    var obj = { a: 123 };
    alert(obj.a);

5. White powers

5.1 Use strict mode

//as first line in js file
"use strict"; 
  
myCodeHere();

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