The arguments parameter

The arguments parameter is a collection of all the arguments passed to the function. The collection has a property named length that contains the count of arguments, and the individual argument values can be obtained using an array indexing notation. Okay, we lied a bit. The arguments parameter is not a JavaScript array, and if you try to use array methods on arguments, you'll fail miserably. You can think of arguments as an array-like structure. This makes it possible to write functions that take an unspecified number of parameters. The following snippet shows you how you can pass a variable number of arguments to the function and iterate through them using an arguments array:

var sum = function () { var i, total = 0; for ...

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