如何获取javascript对象（如窗口而不是字符串[object]）的数值或字符串值

Question

How do I get a numeric or string value for a javascript object such as window instead of the string [object]

Looking for something like an object id, like 44001 or 0xFF0012 that is unique for that object

Answer 1

Javascript doesn't keep a python-like unique hash for each object. You could create a function to assign a unique string to an object, or retrieve the string if it's already been assigned.

var getUniqueId = (function(){

  // uncomment this block if you want to avoid memory leaks
  // in browsers with crappy garbage collectors.
  /*
  try {
    window.addEventListener('unload', cleanup);
    window.addEventListener('beforeunload', cleanup);
  } catch (_) { try {
    window.attachEvent('onunload', cleanup);
    window.attachEvent('onbeforeunload', cleanup);
  } catch (__){}}

  function cleanup () { guid.knownObjects.length=0; }
  */

  guid.knownObjects=[];

  return guid;

  function guid (obj) {
    for (var i=guid.knownObjects.length; i--;) {
      if (guid.knownObjects[i][0]===obj) return guid.knownObjects[i][1];
    }
    var uid='x'+(+(''+Math.random()).substring(2)).toString(32);
    guid.knownObjects.push([obj, uid]);
    return uid;
  }

}());

Testing it out:

getUniqueId(window)
> "x7onn8ne58ug"

getUniqueId(document)
> "x9jeriqjdf9o"

getUniqueId(document)
> "x9jeriqjdf9o"

getUniqueId(window)
> "x7onn8ne58ug"

You can do console.dir(getUniqueId.knownObjects) for some useful debugging info.

getUniqueId.knownObjects
> [
  Array
  0: DOMWindow
  1: "x7onn8ne58ug"
  , 
  Array
  0: HTMLDocument
  1: "x9jeriqjdf9o"
  ]

Answer 2

Javascript has no native support for unique identifiers.

You can change the Object prototype to include one.

Check this thread: JavaScript Object Id

Answer 3

What string representation of window would you expect to see?

Objects which provide a toString implementation to the JS runtime are responsible for their own value. So some object like HTMLElement could return, say, the innerHTML for its toString . But it doesn't, so the default is the type name.

Answer 4

You can write a basic debug like this, where you pass your object as o:

function debug(o){
   var r = '';
   for (var k in o){
      r += k + ' => ' + o[k] + '\n';
   }
   window.alert(r);
}

Or you can search for a dump or print_r eaquivalent like this one: http://geekswithblogs.net/svanvliet/archive/2006/03/23/simple-javascript-object-dump-function.aspx