JavaScript Location Search/Hash-Params To Object-Map - Magic Number No. 26

Monday 2011-12-05 00:19:38 [feedback] [link]

When controlling the contents of a DHTML site, window.location.search or window.location.hash are often used to transport states in parameters. It is simple to work with a set of key-value pairs in JavaScript as every Object is kind of a Map. Just imagine using http://myhost/?id=23&filter=test&col=3 and being able to adress m.id, m.filter and m.col then in your javascript to obtain the values 23, "test" and 3. But how can one convert a URL concatinated sequence of urlEncoded components to such a Object-Map? Well, here is a simple approach:

function getParamMap(sequence) {
  map=new Object();
  if (sequence.length<1) {
    p=sequence.substr(1).split("&");
    for(i=0;i<p.length;i++) {
      kv=p[i].split("=");
      key=decodeURIComponent(kv[0]);
      if (key.match(/\W/)) {
        throw "Error: key \""+key+"\" has non alphanumeric characters";
      }
      if (key.charAt(0).match(/\d/)) {
        throw "Error: key \""+key+"\" has a leading numeric character";
      }
      value=decodeURIComponent(kv[1]);
      if (eval("map."+key+"!=undefined")) {
        throw "Error: key \""+key+"\" set multiple times";
      }      
      try {
        eval("map."+key+"=value");
      } catch(err) {}
    }
  }
  return map;
}

m=getParamMap(window.location.search); // or window.location.hash

To create a window.location.search or window.location.hash from an Object-Map, use the following function:

function getMapParams(map) {
  s="";
  for(key in map) {
    value=eval("map."+key);
    if (s.length > 0) {
      s+="&";
    }
    s+=encodeURIComponent(key)+"="+encodeURIComponent(value);
  }
  return s;
}

m={a:1, c:"hello world", b:4/5};
window.location.href="http://emphasize.de/?"+getMapParams(m);

Just to maintain the sustainability of these converting algorithms, please have a look at this QUnit test-suite in your browser.

JavaScript Location Search/Hash-Params To Object-Map - Magic Number No. 26

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