index.html

---
feature_name: Default parameters (ES2015)
chrome_version: 49
feature_id: 5275456790069248
---

<h3>Background</h3>

<p><a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters'>Default parameters</a> allow formal function parameters to be initialized with default values if no value (or <code>undefined</code>) is supplied.</p>

<p>In ES5, one would test parameter values in the body of the function and assign a value if they were <code>undefined</code>. In ES2015, a check in the function body is no longer required and one can simply defined default values for parameters in the function head.</p>

{% include output_helper.html %}

{% include js_snippet.html filename='demo.js' %}