You must have seen this kind of behavior when you enter console.log() in a browser console window
<pre><code class="lang-javascript">console.log("Hola!")
 Hola!
undefined
</code></pre>
We got two values here:
<ol>
<li>Hola!
</li>
<li>undefined
</li>
</ol>
Even though we expected the first value, the second value came as a surprise.
This is because console.log() function outputs the value of a parameter you pass to it, but it also returns 'undefined' to indicate that the function itself does not have a return value. Therefore, when you use console.log() to output a variable or an expression, the console will display the value of the variable or expression, then print 'undefined' on a new line to indicate that console.log() did not return any value itself.

You must have seen this kind of behavior when you enter console.log() in a browser console window

```javascript
console.log("Hola!")
 Hola!
undefined
```

We got two values here:

1. Hola!
    
2. undefined
    

Even though we expected the first value, the second value came as a surprise.

This is because console.log() function outputs the value of a parameter you pass to it, but it also returns 'undefined' to indicate that the function itself does not have a return value. Therefore, when you use console.log() to output a variable or an expression, the console will display the value of the variable or expression, then print 'undefined' on a new line to indicate that console.log() did not return any value itself.

Why does Chrome/Brave console.log always append a line saying 'undefined'?

Table of contents

No headings in the article.