What are the typical reasons Javascript developed on Firefox fails on IE? [closed]

Answer 1

Please feel free to update this list if you see any errors/omissions etc.

Note: IE9 fixes many of the following issues, so a lot of this only applies to IE8 and below and to a certain extent IE9 in quirks mode. For example, IE9 supports SVG, , and natively, however you must enable standards compliance mode for them to be available.

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General:

• Problems with partially loaded documents: It’s a good idea to add your JavaScript in a window.onload or similar event as IE doesn’t support many operations in partially loaded documents.

• Differing attributes: In CSS, it's elm.style.styleFloat in IE vs elm.style.cssFloat in Firefox. In tags the for attribute is accessed with elm.htmlFor in IE vs elm.for in Firefox. Note that for is reserved in IE so elm['for'] is probably a better idea to stop IE from raising an exception.

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Base JavaScript language:

• Access characters in strings: 'string'[0] isn’t supported in IE as it’s not in the original JavaScript specifications. Use 'string'.charAt(0) or 'string'.split('')[0] noting that accessing items in arrays is significantly faster than using charAt with strings in IE (though there's some initial overhead when split is first called.)

• Commas before the end of objects: e.g. {'foo': 'bar',} aren't allowed in IE.

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Element-specific issues:

• Getting the document of an IFrame:

  • Firefox and IE8+: IFrame.contentDocument (IE started supporting this from version 8.)
  • IE: IFrame.contentWindow.document
  • (IFrame.contentWindow refers to the window in both browsers.)

• Canvas: Versions of IE before IE9 don't support the element. IE does support VML which is a similar technology however, and explorercanvas can provide an in-place wrapper for elements for many operations. Be aware that IE8 in standards compliance mode is many times slower and has many more glitches than when in quirks mode when using VML.

• SVG: IE9 supports SVG natively. IE6-8 can support SVG, but only with external plugins with only some of those plugins supporting JavaScript manipulation.

• and : are only supported in IE9.

• Dynamically creating radio buttons: IE <8 has a bug which makes radio buttons created with document.createElement uncheckable. See also How do you dynamically create a radio button in Javascript that works in all browsers? for a way to get around this.

• Embedded JavaScript in tags and onbeforeunload conflicts in IE: If there's embedded JavaScript in the href part of an a tag (e.g. then IE will always show the message returned from onbeforeunload unless the onbeforeunload handler is removed beforehand. See also Ask for confirm when closing a tab.