CODEWITHSUNDEEP
javascript
YakovL
YakovL

Reputation: 8347

What's the shortest way to repopulate an array by reference?

I have an array which is binded by reference as a model (to handsontable). Let's call it data. At some point I need to recalc it from scratch (let's call a calced new array freshData; it may have a different length). Assigning data = freshData doesn't do the job since this only changes what data references and doesn't alter the binded model. But calling .splice and .push of data does the job:

data.splice(0,data.length);
for(var i = 0; i < freshData.length; i++)
    data.push(freshData[i]);

I wonder: can this be done in a shorter manner? Like, without a loop or may be even using a single method? data.concat(freshData) doesn't help since it creates a new array, it doesn't change data itself. Also, this iterating looks somewhat suboptimal in terms of performance...

Upvotes: 2

Views: 197

Answers (3)

Bergi
Bergi

Reputation: 665100

You can use splice as a oneliner

data.splice(0, data.length, ...freshData);

Alternatively, use data.length = 0 to empty the array and then put in the new data, either using a loop or passing multiple parameters to push. Notice that using spread syntax or apply might overflow the callstack with too large arrays.

Or do it the hard way with assignments:

for (var i=0; i<freshData.length; i++)
    data[i] = freshData[i];
data.length = i;

this iterating looks somewhat suboptimal in terms of performance...

No, there's always a need to iterate in some way or another. The time complexity will be linear to the size of the old and new data. But performance shouldn't be your first concern, focus on readability and correctness. If it's actually a tight spot, do your own comparison benchmark to be sure. I'd suspect that my assignment solution would be the fastest, as it doesn't do a method call and tends to avoid array resizing where possible.

Upvotes: 2

enapupe
enapupe

Reputation: 17049

If you have ES2015 support OR babel:

data.push(...freshData)

Otherwise just go with

data.push.apply(data, freshData);

Upvotes: 2

Arthur Cinader
Arthur Cinader

Reputation: 1602

You can push the whole array at once without the loop:

data.push(...freshData)

https://runkit.com/arthur/59406f521229b300129a7960

Upvotes: 2

Related Questions