title: JavaScript Function Arguments Assignment time: 2015.07.29 09:30:22 layout: post tags:
arguments is a special variable passed to all functions so that actual parameters are accessible even when they are not declared as formal parameters.
{% highlight js %} function a() { console.log(arguments[0], arguments[1]); // a b } a('a', 'b'); {% endhighlight %}
In most cases, arguments is an alias name for formal parameters.
{% highlight js %} function a(x, y) { x = 1; arguments[1] = 2; console.log(arguments[0], arguments[1], x, y); // 1 2 1 2 } a('a', 'b'); {% endhighlight %}
Here's how it goes interesting.
{% highlight js %} a('a', undefined); // 1 2 1 2 a('a'); // 1 2 1 undefined {% endhighlight %}
When an actual parameter is not passed to the function, its behavior is not exactly the same as passing an undefined. A more profound explanation under the hood should be given once I knew more about JavaScript.