In what scenarios is it beneficial to alter the length of a JavaScript array without introducing any new elements?

In this particular query, I discovered that the issue was due to mistakenly incrementing the Array.Prototype.length property using ++

My curiosity lies in why length is not a read-only property of Arrays. Despite it not being an oversight in the language's design, as stated on MDN where it mentions being able to "SET or return" the length of an array. What puzzles me is why one can make such mistakes? What scenario would justify altering the length of an array without modifying the number of elements it holds?

javascriptarrays

Answer №1

I stumbled upon an intriguing article on JavaScriptTutotorial.net that delves into the reasons for utilizing this method.

Clearing an array

By setting the length of an array to zero, you effectively empty the array:

const fruits = ['Apple', 'Orange', 'Strawberry'];
fruits.length = 0;

console.log(fruits); // []

Deleting elements

If you adjust the length property of an array to a lower value than its highest index, it removes elements with indexes greater than or equal to the new length.

For instance, changing the length property of the fruits array to two will eliminate the third element:

const fruits = ['Apple', 'Orange', 'Strawberry'];
fruits.length = 2;

console.log(fruits); // [ 'Apple', 'Orange' ]

Create a sparse array

Setting the length property of an array to a value higher than its highest index results in a sparse array. Here's an example:

const fruits = ['Apple', 'Orange', 'Strawberry'];
fruits.length = 5;

console.log(fruits); // [ 'Apple', 'Orange', 'Strawberry', <2 empty items> ]

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