ArrayLike (AL01)

   1:  // arguments object (from inside a function)

   2:  function myFunction() {

   3:      const args = Array.from(arguments); // Convert arguments to a true array

   4:      args.forEach(arg => console.log(arg));

   5:      const mappedArgs = args.map(x => x * 2); // Now .map() and other array function works

   6:      // ... use any array methods on 'args'

   7:  }

   8:  

   9:  myFunction(1, 2, 3);

In JavaScript, an array-like object is any object that resembles an array but isn't a true Array instance. These objects have the following key characteristics:
    1. length Property: They have a length property that specifies the number of elements they contain. This is numerical non-negative integer value.
    2. Indexed Elements: Their elements are accessible using numerical indices (0, 1, 2, etc.), similar to how you access elements in true arrays using bracket notation (object[0], object[1], etc.)
    3. Lack of Array Methods: Crucially, array-like objects do not have the built-in methods that true arrays possess (e.g., push(), pop(), map(), filter(), forEach()). This is the primary distinction.

Key Differences from True Arrays:
    • Methods: Array-like objects don't have the standard array prototype methods. This makes direct manipulation (e.g., using map, filter) impossible without first converting them to true arrays.
    • Prototype: Their prototype is not Array.prototype.
    • Constructor: Their constructor is not Array.

Converting to a True Array (Most Common):
The Array.from() method is the most straightforward way to convert an array-like object into a true array.

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ArrayLike context:

ES6 context:

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