Function arguments in ECMAScript are defined as special objects acting as arrays. That makes them very flexible in terms of how many of them are being passed to a function. For instance, although a function may be declared with two arguments, the real number of them passed to a function doesn't matter, meaning it can be zero or any number passed and no error will be reported by the script.

Within a function, arguments may be reached by their names (if given) or by their index number within the array called arguments. For instance these two functions will be interpreted equally:

// FUNCTION #1:

function helloWorld("Hello", first, last) {

   alert("Hello" + " " + first + " " + last);

}

// FUNCTION #2:

function helloWorld("Hello", first, last) {

   alert("Hello" + " " + arguments[0] + " " + arguments[1])

}

To check how many arguments are passed to a function, the length property is used:

function helloWorld("Hello", first, last) {

   var args = arguments.length;

}

Example

Example with basic arguments passing to a function:

 

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