Javascript: Error ‘Object Required’. I can’t decipher it. Can you

debuggingflirjavascript

I am using a javascript called 'Facelift 1.2' in one of my websites and while the script works in Safari 3, 4b and Opera, OmniWeb and Firefox it does not in any IE version.
But even in the working browser i get the following error I cannot decipher.

Maybe in due time—with more experience in things Javascript—I will be able to but for now I thought I would ask some of you, here at SO.

The following is the error popup i get in IETester testing the page for Interet Explorer 6,7 and 8:

The following is from the Firebug console in Firefox 3.0.6:

The website is: http://www.457cc.co.nz/index.php In case it helps you see the problem mentioned in action.

I have also looked up what line 620 corresponds to which is:
"line 76" is:

this.isCraptastic = (typeof document.body.style.maxHeight=='undefined');

which is part of this block of code (taken from the flir.js):

// either (options Object, fstyle FLIRStyle Object) or (fstyle FLIRStyle Object)
,init: function(options, fstyle) { // or options for flir style
    if(this.isFStyle(options)) { // (fstyle FLIRStyle Object)
        this.defaultStyle = options;
    }else { // [options Object, fstyle FLIRStyle Object]
        if(typeof options != 'undefined')
            this.loadOptions(options);

        if(typeof fstyle == 'undefined') {
            this.defaultStyle = new FLIRStyle();
        }else {
            if(this.isFStyle(fstyle))
                this.defaultStyle = fstyle;
            else
                this.defaultStyle = new FLIRStyle(fstyle);
        }
    }

    this.calcDPI();

    if(this.options.findEmbededFonts)
        this.discoverEmbededFonts();

    this.isIE = (navigator.userAgent.toLowerCase().indexOf('msie')>-1 && navigator.userAgent.toLowerCase().indexOf('opera')<0);
    this.isCraptastic = (typeof document.body.style.maxHeight=='undefined');

    if(this.isIE) {
        this.flirIERepObj = [];
        this.flirIEHovEls = [];
        this.flirIEHovStyles = [];    
    }
}

The whole script is also available on my server: http://www.457cc.co.nz/facelift-1.2/flir.js

I just don't know where to start looking for the error, especially since it only affects IE but works in the rest. Maybe you guys have an idea. I would love to hear them.

Thanks for reading.
Jannis

PS: This is what Opera's error console reports:

JavaScript - http://www.457cc.co.nz/index.php
Inline script thread
Error:
name: TypeError
message: Statement on line 620: Cannot convert undefined or null to Object
Backtrace:
  Line 620 of linked script http://www.457cc.co.nz/facelift-1.2/flir.js
                    document.body.appendChild(test);
  Line 70 of linked script http://www.457cc.co.nz/facelift-1.2/flir.js
            this.calcDPI();
  Line 2 of inline#1 script in http://www.457cc.co.nz/index.php
            FLIR.init();
stacktrace: n/a; see 'opera:config#UserPrefs|Exceptions Have Stacktrace'

Best Answer

I agree with tvanfosson - the reason you're getting that error is quite likely because you're calling init() before the page is done loading, so document.body is not yet defined.

In the page you linked, you should move the following code to the bottom of the page (just before the closing html tag:

<script type="text/javascript">
    FLIR.init({ path: 'http://www.457cc.co.nz/facelift-1.2/' });
    FLIR.auto();
</script>

Even better, you should attach the initialization to the document's ready event. If you do it this way, there is no need to even move your javascript to the bottom of the file. Using jquery:

$(document).ready( function(){
    FLIR.init({ path: 'http://www.457cc.co.nz/facelift-1.2/' });
    FLIR.auto();
});

More on jquery's document.ready event »

Related Solutions

Javascript – Length of a JavaScript object

The most robust answer (i.e. that captures the intent of what you're trying to do while causing the fewest bugs) would be:

Object.size = function(obj) {
  var size = 0,
    key;
  for (key in obj) {
    if (obj.hasOwnProperty(key)) size++;
  }
  return size;
};

// Get the size of an object
const myObj = {}
var size = Object.size(myObj);

There's a sort of convention in JavaScript that you don't add things to Object.prototype, because it can break enumerations in various libraries. Adding methods to Object is usually safe, though.

Here's an update as of 2016 and widespread deployment of ES5 and beyond. For IE9+ and all other modern ES5+ capable browsers, you can use Object.keys() so the above code just becomes:

var size = Object.keys(myObj).length;

This doesn't have to modify any existing prototype since Object.keys() is now built-in.

Edit: Objects can have symbolic properties that can not be returned via Object.key method. So the answer would be incomplete without mentioning them.

Symbol type was added to the language to create unique identifiers for object properties. The main benefit of the Symbol type is the prevention of overwrites.

Object.keys or Object.getOwnPropertyNames does not work for symbolic properties. To return them you need to use Object.getOwnPropertySymbols.

var person = {
  [Symbol('name')]: 'John Doe',
  [Symbol('age')]: 33,
  "occupation": "Programmer"
};

const propOwn = Object.getOwnPropertyNames(person);
console.log(propOwn.length); // 1

let propSymb = Object.getOwnPropertySymbols(person);
console.log(propSymb.length); // 2

Javascript – the most efficient way to deep clone an object in JavaScript

Native deep cloning

It's called "structured cloning", works experimentally in Node 11 and later, and hopefully will land in browsers. See this answer for more details.

Fast cloning with data loss - JSON.parse/stringify

If you do not use Dates, functions, undefined, Infinity, RegExps, Maps, Sets, Blobs, FileLists, ImageDatas, sparse Arrays, Typed Arrays or other complex types within your object, a very simple one liner to deep clone an object is:

JSON.parse(JSON.stringify(object))

const a = {
  string: 'string',
  number: 123,
  bool: false,
  nul: null,
  date: new Date(),  // stringified
  undef: undefined,  // lost
  inf: Infinity,  // forced to 'null'
  re: /.*/,  // lost
}
console.log(a);
console.log(typeof a.date);  // Date object
const clone = JSON.parse(JSON.stringify(a));
console.log(clone);
console.log(typeof clone.date);  // result of .toISOString()

See Corban's answer for benchmarks.

Reliable cloning using a library

Since cloning objects is not trivial (complex types, circular references, function etc.), most major libraries provide function to clone objects. Don't reinvent the wheel - if you're already using a library, check if it has an object cloning function. For example,

lodash - cloneDeep; can be imported separately via the lodash.clonedeep module and is probably your best choice if you're not already using a library that provides a deep cloning function
AngularJS - angular.copy
jQuery - jQuery.extend(true, { }, oldObject); .clone() only clones DOM elements
just library - just-clone; Part of a library of zero-dependency npm modules that do just do one thing. Guilt-free utilities for every occasion.

ES6 (shallow copy)

For completeness, note that ES6 offers two shallow copy mechanisms: Object.assign() and the spread syntax. which copies values of all enumerable own properties from one object to another. For example:

var A1 = {a: "2"};
var A2 = Object.assign({}, A1);
var A3 = {...A1};  // Spread Syntax