Question

I have a fairly complex piece of Javascript that works flawlessly with no errors in Google Chrome, Firefox, Safari, and Opera. However, as tends to always be the endlessly annoying case, it completely fails in Internet Explorer. I have tested in IE7 and IE8 and get the same error:

Invalid argument. prototype.js, line
2216, character 9

I am using Prototype 1.6.1 hosted through Google. The error given isn’t very helpful since it doesn’t tell me where in my actual code the error is occurring. The line mentioned in the error is the 6th line from the bottom in the following code:

setStyle: function(element, styles) {
    element = $(element);
    var elementStyle = element.style, match;
    if (Object.isString(styles)) {
      element.style.cssText += ';' + styles;
      return styles.include('opacity') ?
        element.setOpacity(styles.match(/opacity:\s*(\d?\.?\d*)/)[1]) : element;
    }
    for (var property in styles)
      if (property == 'opacity') element.setOpacity(styles[property]);
      else
        elementStyle[(property == 'float' || property == 'cssFloat') ?
          (Object.isUndefined(elementStyle.styleFloat) ? 'cssFloat' : 'styleFloat') :
            property] = styles[property];

    return element;
  },

Since it is in the setStyle block of code, I assume the error occurs when I am setting style attributes for some element. However, I call setStyle over 100 times in this script and have been trying to figure out where exactly the error is occurring for several hours. Is there anything I can do to help myself in finding where the error is occurring?

Answer 1

Put an explicit try ... catch around the code:

for (var property in styles) {
  try {
    if (property == 'opacity') element.setOpacity(styles[property]);
    else
      elementStyle[(property == 'float' || property == 'cssFloat') ?
        (Object.isUndefined(elementStyle.styleFloat) ? 'cssFloat' : 'styleFloat') :
          property] = styles[property];
  }
  catch (_) {
    throw "Error setting property '" + property + "' to value '" + styles[property] + "'";
  }
}

Then you’ll know exactly what property and value is causing the problem.