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, Sep 24 '14 at 13:59

score 1 · Answer 1 · edited May 23 '17 at 12:21

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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 '17 at 12:21

Community

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answered Sep 24 '14 at 11:56

Frederik Wordenskjold

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And also set it via `array.length` – CodingIntrigue Sep 24 '14 at 11:58
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? – elbereth Sep 24 '14 at 13:32
Yeah, it would. But as mentioned, it is probably not necessary. – Frederik Wordenskjold Sep 24 '14 at 13:48

score 0 · Answer 2 · answered Sep 24 '14 at 11:58

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"]

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ArrayList.ensureCapacity equivalent in Javascript

2 Answers2