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javascriptperformanceenumsintegerswitch-statement
Putzi San
Putzi San

Reputation: 6301

JavaScript Performance switch (Integer) vs switch (String)

I'm coming from C# and there it's a huge different between
A:

var stringVal = "1";
switch (stringVal)
{
    case "0" :
    break;
    case "1" :
    break;
}

and
B:

var intVal = 1;
switch (intVal)
{
    case 0 :
    break;
    case 1 :
    break;
}

B is much faster in C# (cause the String-Switch will converted to if-else-structure from the compiler).

Is it in JavaScript similar? (Of course there is just the number-type in JS)

And - for readability - if i want to use it with some enum-"equivalent" in JS (like described here http://stijndewitt.com/2014/01/26/enums-in-javascript/), is there a anyway performance-improvement when using 

var caseEnum = {
    firstCase : 0,
    secCase : 1
}

var enumVal = caseEnum.secCase ;
switch (enumVal )
{
    case caseEnum.firstCase :
    break;
    case caseEnum.secCase :
    break;
}

?

(I know that i could do it with object literals, but the switch-statement with integer is more naturally for me)

Upvotes: 4

Views: 1863

Answers (2)

Putzi San
Putzi San

Reputation: 6301

I did a little incredible ugly Test on my own
( look at:https://jsfiddle.net/PutziSan/kzdwt8u2 )

and run the code on different browsers (results below), (all the browsers was updated on the latest version today - 03.01.2016)

by the way another hint, that edge and IE is just ridiculous.
The results are realy interesting, i guess.
(I know this sort of "tests" are not that accurate, but i think they can give a hint)

It seems, that switch with Integer is noticed from the compilers, but it has not that great impact.

chrome:
chrome

firefox:
firefox

edge:
edge

IE:
IE

Upvotes: 4

CodeWizard
CodeWizard

Reputation: 141986

Is it in JavaScript similar? (Of course there is just the number-type in JS)

In javascript the expression can be almost anything, its not like in C where the type is verified during compilation, here its being calculated during "runtime"

That's the main difference.

A very detailed explanation is in the MDN - Switch

... expression evaluates to the same value as the result of the input expression
(using strict comparison, ===)

... is there a anyway performance-improvement

It depends on your browser and its JS engine.

Upvotes: 0

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