d to as <em>static</em> checking.
Determining what's an error and what's not based on the kinds of values being operated on is known as <em>type</em> checking.</p>
<p>Because TypeScript checks a program for errors before it's run, and does so based on the <em>kinds of values</em>, it's a <em>static type checker</em>.
For example, the snippet from earlier has an error because of the <em>type</em> of <code>obj</code>.
Here's the error TypeScript found:</p>
<p><pre class="typescript-code"><span class="tm-kw">c