Javascript – building a wysiwyg editor

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I need to build a wysiwyg editor for a project I am working on and need some guidance. Some of my key points of confusion are the following:

iframe docs vs. contenteditable divs: which one should I use and why? I hate iframes, is there a clear advantage to using iframes?

cross browser styling: execCommand seems to apply different styles in different browsers. Are there any tricks to making this cross-browser compatible? Should I not use execCommand at all and instead apply my own styles?.

adding items to the undo chain: how can run my own script, such as inserting an image, and allow cntrl+z (undo) to remove it? Is there an array of undo/redo items for contenteditable that I can push items into?

keeping the text selection: how I can maintain text selection while making operations such as selecting the font style, where the focus will leave and remove my selection. Rangy? Google closure? Are there other range/selection libraries worth looking at?

Any tips on these items or anything else related to building a rich text editor would be greatly appreciated!

Best Answer

From personal experience, I recommend against doing this unless your aim is to provide a very limited amount of functionality. The sheer number of browser differences and the complexity of their workarounds makes this a very tricky and time-consuming task if you want to do it well.

If that hasn't put you off, here's my thoughts on your individual questions:

iframe docs vs. contenteditable divs

I recommend the iframe approach, for two main reasons:

You have complete control over the document type, CSS and script within the iframe. This is essential if you want consistent behaviour and appearance and want to use your editor within different pages.
Firefox in particular is quite buggy with contenteditable elements, which they only introduced relatively recently (version 3.0) while designMode has existed on documents for many years (since pre-1.0; around 0.6, if memory serves) and works pretty well.

cross browser styling

If it's important for you to have uniform results from applying styles in different browsers then in general you will need to write your own styling code. However, doing this will break the built-in undo stack and you will need to implement your own undo/redo system.

adding items to the undo chain

There's no programmatic way to interact with the built-in browser undo stack. You'll need to write your own.

Update November 2012

There is a spec in the works for custom undo/redo so this is likely to be possible eventually. Here are the relevant bugs for Mozilla and WebKit.

keeping the text selection

I have to declare my interests here, since I wrote Rangy. I don't think there's a better library out there that does a similar job; Google Closure does have a range/selection API but I think it uses their own proprietary interface rather than emulating DOM Range and common browser Selection objects. IERange is another library that is similar in idea to Rangy but much less fully realized and seemingly abandoned immediately after release by its author.

Related Solutions

Css – Override body style for content in an iframe

The below only works if the iframe content is from the same parent domain.

The following jquery script works for me. Tested on Chrome and IE8. The inner iframe references a page that is on the same domain as the parent page.

In this particular case, I am hiding an element with a specific class in the inner iframe.

Basically, you just append a style element to the head section of the document loaded in a frame:

frame.addEventListener("load", ev => {
    const new_style_element = document.createElement("style");
    new_style_element.textContent = ".my-class { display: none; }"
    ev.target.contentDocument.head.appendChild(new_style_element);
});

You can also instead of style use a link element, for referencing a stylesheet resource.

Javascript – ContentEditable – Get current font color/size

You can use document.queryCommandValue() to get the colour and font size of the current selection in all major browsers:

Live demo: http://jsfiddle.net/timdown/AJBsY/

Code:

var colour = document.queryCommandValue("ForeColor");
var fontSize = document.queryCommandValue("FontSize");

However, the results are inconsistent across browsers and the FontSize command only works with font sizes 1-7 used in the HTML <font> element rather than CSS, so you'd be better off getting hold of the element containing the selection and examining its CSS properties using window.getComputedStyle() / currentStyle:

Live demo: http://jsfiddle.net/timdown/K4n2j/