I have a theory that a JavaScript array functions as a hashmap, only accepting integral values as keys. Also, the .length property simply returns the largest index + 1.
Is my understanding correct? Are there any other distinctions to note?
I have a theory that a JavaScript array functions as a hashmap, only accepting integral values as keys. Also, the .length property simply returns the largest index + 1.
Is my understanding correct? Are there any other distinctions to note?
Incorrect! Arrays can actually have keys of your choice.
Furthermore, they also take on the Array prototype.
The distinction is evident in the output:
Object.prototype.toString.call([]); // [object Array]
Object.prototype.toString.call({}); // [object Object]
Update:
Furthermore, take a look at this portion from ECMAScript guidelines as it precisely defines what constitutes an Array:
When it comes to JavaScript, an array inherits from Object and therefore has access to all of the capabilities associated with objects. However, arrays have some additional functionality that sets them apart:
var myA = ['foo', 'bar', 'baz'];
var myO = {0: 'foo', 1: 'bar', 2: 'baz'};
// Both lines below will output "foo":
console.log(myA[0]);
console.log(myO[0]);
// Arrays also have unique methods:
console.log(myA.pop());
console.log(myO.pop()); // <- results in an error
While it is possible to add integer properties to regular Objects and non-integer properties to Arrays, doing so does not provide the object with the special properties and methods specific to arrays. The special features of arrays only apply to elements with integer keys.
For a comprehensive list of the additional properties inherited by arrays, refer to the Mozilla Developer Center article on Array. Take note of the "non-standard" and "Requires JavaScript 1.x" annotations for maintaining compatibility across various browsers.
Arrays can hold any property that regular objects can hold. The key distinguishing feature is the "length" property, which automatically updates when you add or remove array elements by setting an index value.
Array indices are represented as strings, specifically as decimal representations of unsigned integers ranging from 0 to 4294967294 (i.e., "0" to "4294967294"). This limitation ensures that the length field value remains within the bounds of a 32-bit unsigned integer.
All array objects inherit from Array.prototype and belong to the internal class "Array." Essentially, the main distinction between Arrays and regular Objects lies in the presence of the special "length" property. If this feature isn't necessary for your purpose, utilizing a plain Object may be more suitable.
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