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QL code and tests for C#/C++/JavaScript.

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Pavel Avgustinov
2018-08-02 17:53:23 +01:00
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javascript/ql/src/Statements/UselessConditional.qhelp Normal file
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<!DOCTYPE qhelp PUBLIC
"-//Semmle//qhelp//EN"
"qhelp.dtd">
<qhelp>
<overview>
<p>
If a condition always evaluates to true or always evaluates to false, this often indicates
incomplete code or a latent bug and should be examined carefully.
</p>
</overview>
<recommendation>
<p>
Examine the surrounding code to determine why the condition is useless. If it is no
longer needed, remove it.
</p>
</recommendation>
<example>
<p>
The following example constructs an array <code>lines</code>, and then attempts to check whether
it has any elements by means of an if conditional <code>if (!lines)</code>.
</p>
<sample src="examples/UselessConditional.js" />
<p>
Note that in JavaScript (unlike some other languages) arrays and objects are always considered to
be true when evaluated in a Boolean context. The code should instead check <code>lines.length</code>:
</p>
<sample src="examples/UselessConditionalGood.js" />
</example>
<references>
<li>Mozilla Developer Network: <a href="https://developer.mozilla.org/en-US/docs/Glossary/Truthy">Truthy</a>,
<a href="https://developer.mozilla.org/en-US/docs/Glossary/Falsy">Falsy</a>.</li>
</references>
</qhelp>