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updating the Function Binding docs with an improved explanation.

This commit is contained in:
Jeremy Ashkenas 2010-03-06 19:29:41 -05:00
parent c73a3ec356
commit 87420e6504
2 changed files with 26 additions and 0 deletions
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13
documentation/index.html.erb
View File

@ -649,6 +649,14 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
<p>
<span id="fat_arrow" class="bookmark"></span>
<b class="header">Function binding</b>
In JavaScript, the <tt>this</tt> keyword is dynamically scoped to mean the
object that the current function is attached to. If you pass a function as
as callback, or attach it to a different object, the original value of <tt>this</tt>
will be lost. If you're not familiar with this behavior,
<a href="http://www.digital-web.com/articles/scope_in_javascript/">this Digital Web article</a>
gives a good overview of the quirks.
</p>
<p>
The fat arrow <tt>=></tt> can be used to both define a function, and to bind
it to the current value of <tt>this</tt>, right on the spot. This is helpful
when using callback-based libraries like Prototype or jQuery, for creating
@ -657,6 +665,11 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
properties of the <tt>this</tt> where they're defined.
</p>
<%= code_for('fat_arrow') %>
<p>
If we had used <tt>-></tt> in the callback above, <tt>@customer</tt> would
have referred to the undefined "customer" property of the DOM element,
and trying to call <tt>purchase()</tt> on it would have raised an exception.
</p>
<p>
<span id="embedded" class="bookmark"></span>

13
index.html
View File

@ -1400,6 +1400,14 @@ city = _c[1];
<p>
<span id="fat_arrow" class="bookmark"></span>
<b class="header">Function binding</b>
In JavaScript, the <tt>this</tt> keyword is dynamically scoped to mean the
object that the current function is attached to. If you pass a function as
as callback, or attach it to a different object, the original value of <tt>this</tt>
will be lost. If you're not familiar with this behavior,
<a href="http://www.digital-web.com/articles/scope_in_javascript/">this Digital Web article</a>
gives a good overview of the quirks.
</p>
<p>
The fat arrow <tt>=></tt> can be used to both define a function, and to bind
it to the current value of <tt>this</tt>, right on the spot. This is helpful
when using callback-based libraries like Prototype or jQuery, for creating
@ -1427,6 +1435,11 @@ Account <span class="Keyword">=</span> <span class="Storage">function</span> <sp
})(<span class="Variable">this</span>));
};
</pre><br class='clear' /></div>
<p>
If we had used <tt>-></tt> in the callback above, <tt>@customer</tt> would
have referred to the undefined "customer" property of the DOM element,
and trying to call <tt>purchase()</tt> on it would have raised an exception.
</p>
<p>
<span id="embedded" class="bookmark"></span>