Fix “Handling text — strings in JavaScript” typo

Fixes #2959

files/en-us/learn/javascript/first_steps/strings/index.html

@@ -153,7 +153,7 @@ <h3 id="Numbers_vs._strings">Numbers vs. strings</h3>
    <li>Conversely, every number has a method called <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toString">toString()</a></code> that converts it to the equivalent string. Try this:
     <pre class="brush: js">let myNum2 = 123;
 let myString2 = myNum2.toString();
-typeof myString;</pre>
+typeof myString2;</pre>
    </li>
   </ul>
   These constructs can be really useful in some situations. For example, if a user enters a number into a form's text field, it's a string. However, if you want to add this number to something, you'll need it to be a number, so you could pass it through <code>Number()</code> to handle this. We did exactly this in our <a href="https://github.com/mdn/learning-area/blob/master/javascript/introduction-to-js-1/first-splash/number-guessing-game.html#L54">Number Guessing Game, in line 54</a>.</li>