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<qhelp>

<overview>

<p>

A <code>finally</code> block is normally used to perform cleanup operations at the end of a

<code>try</code> statement; it is run no matter which way the associated <code>try</code> statement

terminates: successful termination, a <code>return</code> statement, or an exception being thrown.

</p>

<p>

If a <code>finally</code> block contains a <code>return</code> statement or a <code>break</code>

or <code>continue</code> statement referring to a loop outside the <code>try</code> statement,

this statement will jump out of the <code>finally</code> block, thus overriding any return value

or exception throw arising from the <code>try</code> statement. This is often unintentional, and

in any case makes the code hard to read.

</p>

</overview>

<recommendation>

<p>

Carefully inspect all possible control flow paths through the <code>try</code> statement and

its <code>finally</code> block. If the jump out of the <code>finally</code> block is unintentional,

then correct it. If it is intentional, restructure the code to move the jump into the main

<code>try</code> block instead.

</p>

</recommendation>

<example>

<p>

The following code snippet contains a <code>try</code> statement that acquires a resource and then

performs an action on it. However, if the condition checked by function <code>someCond</code>

holds, an <code>Error</code> is thrown instead of performing the action. The <code>finally</code>

block releases the resource, and returns <code>true</code> if <code>someOtherCond</code> returns

<code>true</code>.

</p>

<p>

Note that if <code>someCond</code> and <code>someOtherCond</code> both return <code>true</code>,

the exception thrown on line 5 is suppressed by the <code>return</code> statement on line 10.

</p>

<sample src="examples/JumpFromFinally.js" />

<p>

If the suppression of the thrown exception is intentional, the check for <code>someOtherCond</code>

should be moved into the <code>try</code> statement like this:

</p>

<sample src="examples/JumpFromFinallyGood.js" />

<p>

While this transformation leads to some code duplication, it makes the control flow more explicit

and easier to understand.

</p>

</example>

<references>

<li>Mozilla Developer Network: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try...catch">try...catch</a>.</li>

</references>

</qhelp>