VARIADIC FUNCTIONS IN JAVASCRIPT

KERALA JS USER GROUP MEETUP - SEPT 2014

github.io/akhilstanislavose

Variadic What?

In computer programming, a variadic function is a function of indefinite arity, i.e., one which accepts a variable number of arguments.

 

- Wikipedia

The best example!

 #include <stdio.h>

 int main(){
   printf("Hello world!");
   return 0;
 }

Function Arguments

 var concat = function(arg) {
   return arg;
 }

Arguments Object

The arguments object is an Array-like object corresponding to the arguments passed to a function.

- MDN JavaScript Reference

...

 var whatAreTheParameters = function() {
   return arguments;
 }

 whatAreTheParameters()
 //=> []

 whatAreTheParameters(1)
 //=> [1] 

 whatAreTheParameters(1, 'two', 3.0)
 //=> [1, 'two', 3]

Concat Function

 var concat = function() {
    var result = '';
    
    for(var i=0; i < arguments.length; i++)
      result += arguments[i];

    return('' == result ? undefined : result);
 }

 concat('Hello ', 'world');
 //=> 'Hello world!'

List Function

  var list = function(type) {
    var result = '<' + type + 'l><li>';
    var args = Array.prototype.slice.call(arguments, 1);
    result += args.join('</li><li>');
    result += '</li></' + type + 'l>';
  
    return result;
  }

  list('u', 'one', 'two');
  //=> '<ul><li>one</li><li>two</li></ul>'

ECMAScript 6

Rest Parameters

  var list = function(type, ...args) {
    var result = '<' + type + 'l><li>';
    result += args.join('</li><li>');
    result += '</li></' + type + 'l>';
  
    return result;
  }

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters

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