ArrayList.ensureCapacity equivalent in Javascript

Question

Is there an equivalent method in Javascript arrays or ArrayList to Java's ensureCapacity? I am translating a certain Java code containing this method to Javascript, and couldn't find any equivalent to it. Thanks in advance

No, there is no official one, but engines are pretty smart anyway. Some of them have an optimisation to pre-allocate memory when you assign a .length, but it doesn't make much difference. — Bergi
– Bergi, Commented Sep 24, 2014 at 13:59

Community · Accepted Answer · 2017-05-23 12:21:40Z

1

It is possible to initialize an array with a specific size:

var array = new Array(n);

If your array has already been initialized you can, as mentioned in comments, set the length of the array using the length property:

array.length = n;

However, the performance gains, if any, seems negligble. Here is a thread discussing this.

edited May 23, 2017 at 12:21

CommunityBot

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answered Sep 24, 2014 at 11:56

Frederik Wordenskjold

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3 Comments

CodingIntrigue Over a year ago

And also set it via array.length

elbereth Over a year ago

So, for instance, if I am using it this way: public Path(int initialCapacity) { tsIindexes.ensureCapacity(initialCapacity); tsJindexes.ensureCapacity(initialCapacity); } would setting it with length amount to the same thing as done here?

Frederik Wordenskjold Over a year ago

Yeah, it would. But as mentioned, it is probably not necessary.

user2575725 · Accepted Answer · 2014-09-24 11:58:40Z

0

var fruits = ['apple', 'pineapple'];
console.log(fruits.length, fruits);//2 ["apple", "pineapple"] 
fruits.length = fruits.length + 4; //increase by 4
console.log(fruits.length, fruits);//6 ["apple", "pineapple"]

Open console for more ...

answered Sep 24, 2014 at 11:58

user2575725

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