Revision 1028914 of Warning: unreachable code after return statement

<div>{{jsSidebar("Errors")}}</div>

<h2 id="Message">Message</h2>

<pre class="syntaxbox">
Warning: unreachable code after return statement (Firefox)
</pre>

<h2 id="Error_Type">Error Type</h2>

<p>Warning</p>

<h2 id="What_went_wrong">What went wrong?</h2>

<p>You were either:</p>

<ul>
 <li>using an expression after a {{jsxref("Statements/return", "return")}} statement</li>
 <li>using a semicolon-less return statement but including an expression directly after</li>
</ul>

<p>When an expression exists after a valid return statement, a warning is given to indicate that the code after the return statement is unreachable, meaning it can never be run.</p>

<p>Why should I have semicolons after <code>return</code> statements? In the case of semicolon-less return statements, it can be unclear whether the developer intended to return the statement on the following line, or to stop execution and return. The warning&nbsp;indicates that there is ambiguity in the way the return statement is written.</p>

<p>Warnings will not be shown for semicolon-less returns if these statements follow it:</p>

<ul>
 <li>throw</li>
 <li>break</li>
 <li>var</li>
 <li>function</li>
</ul>

<h2 id="Examples">Examples</h2>

<h3 id="Invalid_cases">Invalid Cases</h3>

<pre class="brush: js example-bad">
function f() {
  var x = 3;
  x += 4;
  return x;   // return exits the function immediately
  x -= 3;     // so this line will never run; it is unreachable
}

function f() {
  return     // <span class="author-a-z71z8yd1z76zaz69zxz76zz65z614z74zz71z">this is treated like `return;`</span>
    3 + 4;   // so the function returns, and this line is never reached
}
</pre>

<h3 id="Valid_cases">Valid cases</h3>

<pre class="brush: js example-good">
function f() {
  var x = 3;
  x += 4;
  x -= 3;
  return x;  // ok: return after all other statements
}

function f() {
  return 3 + 4  // ok: semicolon-less return with expression on the same line
}
</pre>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Statements/return", "Automatic Semicolon Insertion", "#Automatic_Semicolon_Insertion")}}</li>
</ul>