javascript

Chapter 13: Scripting Forms
Note that even when commands are supported across all browsers, the HTML that the commands
produce is often very different. For instance, applying the bold command surrounds text with < strong >
in IE and Opera, with < b > in Safari and Chrome, and with a < span > in Firefox. You cannot rely on
consistency in the HTML produced from a rich text editor, due to both command implementation and
the transformations done by innerHTML .
There are some other methods related to commands. The first is queryCommandEnabled() , which
determines if a command can be executed given the current text selection or caret position. This method
accepts a single argument, the command name to check, and returns true if the command is allowed
given the state of the editable area, or false if not. Consider this example:
var result = frames[“richedit”].document.queryCommandEnabled(“bold”);
This code returns true if the “ bold ” command can be executed on the current selection. It ’s worth
noting that queryCommandEnabled() does not indicate if you are allowed to execute the command, but
only if the current selection is appropriate for use with the command. In Firefox, queryCommandEnabled
( “ cut “ ) returns true even though it isn ’ t allowed by default.
The queryCommandState() method lets you determine if a given command has been applied to the
current text selection. For example, to determine if the text in the current selection is bold, the following
can be used:
var isBold = frames[“richedit”].document.queryCommandState(“bold”);
If the “ bold ” command was previously applied to the text selection, then this code returns true . This is
the method by which full - featured rich text editors are able to update buttons for bold, italic, and so on.
The last method is queryCommandValue() , which is intended to return the value with which a
command was executed (the third argument in execCommand in the earlier example). For instance, a
range of text that has the “ fontsize ” command applied with a value of 7 returns “ 7 ” from the
following:
var fontSize = frames[“richedit”].document.queryCommandValue(“fontsize”);
This method can be used to determine how a command was applied to the text selection, allowing you
to determine whether the next command is appropriate to be executed.
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