does size of argument in a javascript function affects its performance?

Question

I have a key value pair containing five keys with values as huge array of thousand objects each . I can either subset it while passing it into a function or i can pass whole array in the function.

For e.g:

keyVal ={"first_array": Object[1000],
"second_array": Object[1000],
"third_array": Object[1000],
"fourth_array": Object[1000]
}
var first_arr = keyVal.first_array

Two possibilities:

function notSubsettedArgs(keyVal){
$.each(keyVal.first_array,function(i,item){
//some processing});
}

function subsettedArgs(first_array){
$.each(first_array,function(i,item){
//do some processing});
}

Does it make difference in javascript ?
Does function takes the load of size of arguments ?
Thanks

since it appears that the data will live before and after the function call in question, it likely makes no difference, you're passing "pointers" either way. — dandavis, Apr 28 '15 at 18:50
yes, it's like that. don't get too specific with semantics, or we'll be here all day, but when you pass an object in js, you essentially pass a ref to the object. if the processing isn't preventing garbage collection, the cpu/ram usage should be constant. — dandavis, Apr 28 '15 at 18:51
It's possible that the only performance hit you might get is using jQuery's `each` instead of JS native functions. I've not tested this tho, so take it with a pinch of salt. — Andy, Apr 28 '15 at 18:52
@Andy: in both cases, $.each() is passed the exact same thing... — dandavis, Apr 28 '15 at 18:53
performance is measured it time, so start a timer before you call a function with a big parameter, compared to a small parameter. — DLeh, Apr 28 '15 at 18:55

Trott · Accepted Answer · 2015-04-28T19:20:12.620

7

JavaScript passes arrays and objects to functions by passing a copy of the reference to the array/object, so it is likely to be fine to pass the whole thing. Just know that if you mutate it in the function, those changes will affect your original array/object!

If this is browser code and not server (e.g., Node.js) code, you can test with jsperf.com. Just be careful. It's easy to do JS benchmarks wrong!

edited Apr 28 '15 at 19:20

answered Apr 28 '15 at 18:53

Trott

66,479
23
173
212

*"JavaScript passes arrays and objects to functions by reference"* To be more precise, JavaScript passes everything by *value*, but the value is a reference to an object. That's different from the actual meaning of *pass by reference*. – Felix Kling Apr 28 '15 at 19:16
1

Thanks. I've tried to make the language more precise: "JavaScript passes arrays and objects to functions by passing a copy of the reference to the array/object" – Trott Apr 28 '15 at 19:20

does size of argument in a javascript function affects its performance?

1 Answers1

Linked