Something something

• map( ) for Javascript objects

  2 years ago

  I recently had use for a map()-function while writing Javascript. Javascript has Array.map(), and jQuery has $.map(), but those only works on arrays, and I needed one that could do its magic on objects. So I wrote this one:

  function mapObj(obj, fun) {
    var ret = {};
    for (i in obj) {
      if (obj.hasOwnProperty(i)) {
        fun.call({emit: function(key, value) {
          ret[key] = value;
        }}, i, obj[i]);
      }
    }
    return ret;
  }
  

  mapObj() takes an object and a function, applies the function to each property of the object, gathers up the result and returns it as a new object. The function supplied to mapObj is called with two parameters, the key and value of the current property. To add properties to the final object, call this.emit(key, value) from the function. This may be called any number of times for each property (including zero).

  Here’s a usage example:

  var obj = {a:1, b:2, c:3, d:4};
  var obj2 = mapObj(obj, function(key, val) {
    if (val != 2) {
      this.emit(key.toUpperCase(), val*2);
    } else {
      this.emit(key, val);
      this.emit('aaa', 'bbb');
    }
  });
  // {A:2, b:2, aaa:'bbb', C:6, D:8}
  

  Maybe someone will find this useful.

  #

So what’s all this then

My name is Arne Martin Aurlien. I run this thing. Here’s a few facts about me:

• I work as some kind of software developer at Boost Communications
• I write HTML and Javascript and PHP also other things
• I like HTML5 and jQuery
• I live in Trondheim, Norway
• I have Veronicaa wife
• I’m on Twitter
• I’m also on GitHub
• Send me an am@aurlien.nete-mail

Here’s a few things I have made:

• Piknik: A pretty, jQuery-based color picker webapp thing
• Flickable.js: A Javascript-library for creating flickable image galleries on touch-enabled devices
• SafariKeywordSearch: A Safari extension for keyword search
• Some pretty flowers
• The Bacon Pie