<!DOCTYPE qhelp PUBLIC
 "-//Semmle//qhelp//EN"
 "qhelp.dtd">
<qhelp>
<overview>
<p>
Most popular JavaScript platforms support <code>const</code> declarations, although this feature is not
part of the ECMAScript 5 standard. Assigning a new value to a variable that is declared <code>const</code>
does not result in an error on current platforms, and simply has no effect. Relying on this behavior is
error-prone, particularly since ECMAScript 2015 prohibits such assignments.
</p>

</overview>
<recommendation>

<p>
If the variable genuinely needs to be reassigned, change its declaration from <code>const</code> to
<code>var</code>, or merge the assignment into the variable declaration, if possible. Otherwise, remove
the spurious assignment.
</p>

</recommendation>
<example>

<p>
In the following example, <code>loc</code> is initialized to <code>null</code>, and then set to
either <code>"here"</code> or <code>"there"</code>, depending on the value of variable <code>dist</code>.
Most current platforms, however, will ignore the assignments entirely, so <code>loc</code> will retain
its original value <code>null</code>.
</p>

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

<p>
Instead, the assignments to <code>loc</code> can be merged into its declaration like this:
</p>

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

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