In the last article, we discussed default parameters in javascript. In this article, we’ll discuss javascript arguments parameter objects.

For a function like this, how do we do different things depending on the parameters we pass in?

function addAll () {
    // What do we do here?
}
// Should return 6
addAll(1, 2, 3);
// Should return 10
addAll(1, 2, 3, 4);

Fortunately, javascript has a arguments object that handles the above situation. The arguments object is a class array object. For more information about the arguments object, please click here. We use the arguments object to change the above example:

function addAll () {
    var sum = 0;
    for (var i = 0; i < arguments.length; i++) {
        sum += arguments[i];
    }
    return sum;
}
// Returns 6
addAll(1, 2, 3);
// Returns 10
addAll(1, 2, 3, 4);

We said above that the arguments object is an array of class objects, let’s test it:

function getName() {
 console.log(Array.isArray(arguments));
}
//will output false
getName("benjamin");

The above test results can be seen: It’s not an array object, so how is it different from an array object? Please click here for details.

Executing the following example throws an error:

function sortArgs () {
    // Uncaught TypeError: undefined is not a function
    sorted = arguments.sort()
    return sorted;
}
sortArgs();

We can convert an array object into an array object as follows:

function sortArgs () {
    // Convert arguments object into a real array
    var args = [].slice.call(arguments);
    // Now this will work!
    sorted = args.sort()
    return sorted;
}
//will output [1, 2, 3]
console.log(sortArgs(1,3,2));