over.js

Elegant function overloading in JavaScript.

Example

Just wrap your functions with the Over() method, and use special argument names to denote types:

var obj = {

  /**
   * Says something in the console.
   *
   * say(msg) - Says something once.
   * say(msg, times) - Says something many times.
   */
  say: Over(

    // one string
    function(msg$string){

      // say it in the console
      console.info(msg$string);

    },

    // a string and a number
    function(msg$string, times$number){

      // say the message times$number times
      for (var i = 0; i < times$number; i++) this.say(msg$string);

    },

    // then everything else
    function(msg$string, everything$etc) {

      // say the string
      this.say(msg$string);

      // now say all remaining arguments
      for (var i in everything$etc) {
        this.say(everything$etc[i])
      }

    }
  )

};

Argument names

[name]${test}

The argument name contains any name (optional), followed by a $ literal, followed by the type of test that will take place when checking the signature of the function.

Built in tests:

• $string - Checks whether the argument is a string or not.
• $number - Checks whether the argument is a number or not.
• $object - Checks whether the argument is an object or not (not an array).
• $array - Checks whether the argument is an array or not.
• $bool | $boolean - Checks whether the argument is a boolean or not (i.e. true or false).
• $function - Checks whether the argument is a function or not.
• $nothing - Checks whether the argument is null or undefined.
• $null - Checks whether the argument is null or not.
• $undefined - Checks whether the argument is undefined or not.

The special $etc kind

If you use anything$etc, it will allow any kind of argument (or no argument at all), and any arguments following it. All remaining arguments will be collected into an array, which will become the value for anything$etc. So you can check for the length of additional arguments by doing anything$etc.length.

Adding your own

You can add your own tests by simply adding a function to the Over.is object. For example, to add support for checking if an argument is a positive number, you could do:

Over.is.positiveNumber = function(v){ return Over.is.number(v) && v > 0; };