What is the Mechanism Behind Array.prototype.slice.call\'s Argument Transformation?

The Inner Workings of Array.prototype.slice.call: Demystifying Argument Transformation

It's commonly known that Array.prototype.slice.call(arguments) enables arguments to be treated as an actual array. However, the intricate workings behind this transformation remain a mystery to many. Let's delve into the technicalities to fully grasp its functionality.

Normally, when calling the .slice() method, its target is an array. It iterates through the array and performs its intended operations.

But what happens when .slice() is invoked with something that's not an actual array? This is where the magic of Array.prototype.slice.call comes into play.

By utilizing the .call() method, we manually define the this value for the .slice() function. This gives us the ability to pass any object that resembles an array, even a plain one like my_object shown below:

var my_object = {
    '0': 'zero',
    '1': 'one',
    '2': 'two',
    '3': 'three',
    '4': 'four',
    length: 5
};

As long as the object has a .length property and behaves like an array in terms of numerical indices, it tricks .slice() into performing its intended operations.

Consider the example provided:

var sliced = Array.prototype.slice.call( my_object, 3 );

The result, as expected, is ['three','four'], demonstrating that .slice() has seamlessly extracted the desired elements from our makeshift array.

In essence, Array.prototype.slice.call(arguments) leverages object substitution to empower the .slice() function to handle arguments as if they were a genuine array. This allows us to transform arguments into a well-behaved array for further manipulation.

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