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Message from discussion somewhat OT: creating a lookup hash in JS
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Ted Young  
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 More options Oct 30 2012, 7:35 pm
From: Ted Young <t...@radicaldesigns.org>
Date: Tue, 30 Oct 2012 16:35:43 -0700
Local: Tues, Oct 30 2012 7:35 pm
Subject: Re: [nodejs] Re: somewhat OT: creating a lookup hash in JS
Print | View thread | Show original | Report this message | Find messages by this author

var MAX = 1000000;
var arr = [], obj = {}, obj2 = {},foo, start;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

start = Date.now();
arr.reduce(function(obj2,i){
    obj2[i] = true;
    return obj2;
},obj2);

console.log('reduce',Date.now() - start);

start = Date.now();
arr.forEach(function(i){
    obj[i] = true;

});

console.log('forEach',Date.now() - start);
var MAX = 1000000;
var arr = [], obj = {}, obj2 = {},foo, start;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

start = Date.now();
arr.reduce(function(obj2,i){
    obj2[i] = true;
    return obj2;
},obj2);

console.log('reduce',Date.now() - start);

start = Date.now();
arr.forEach(function(i){
    obj[i] = true;

});

console.log('forEach',Date.now() - start);
var MAX = 1000000;
var arr = [], obj = {}, obj2 = {},foo, start;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

start = Date.now();
arr.reduce(function(obj2,i){
    obj2[i] = true;
    return obj2;
},obj2);

console.log('reduce',Date.now() - start);

start = Date.now();
arr.forEach(function(i){
    obj[i] = true;

});

console.log('forEach',Date.now() - start);
A quick speed test, comparing forEach and reduce:

var arr = [], obj = {}, obj2 = {}, start;
var MAX = 1000000;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

// test reduce
start = Date.now();
arr.reduce(function(obj,i){
    obj[i] = true;
    return obj;
},obj);

console.log('reduce',Date.now() - start);

// test forEach
start = Date.now();
arr.forEach(function(i){
    obj2[i] = true;

});

console.log('forEach',Date.now() - start);
var MAX = 1000000;
var arr = [], obj = {}, obj2 = {},foo, start;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

start = Date.now();
arr.reduce(function(obj2,i){
    obj2[i] = true;
    return obj2;
},obj2);

console.log('reduce',Date.now() - start);

start = Date.now();
arr.forEach(function(i){
    obj[i] = true;

});

console.log('forEach',Date.now() - start);
var MAX = 1000000;
var arr = [], obj = {}, obj2 = {},foo, start;

for(i = 0; i < MAX; i++){
  arr.push(i.toString());

}

start = Date.now();
arr.reduce(function(obj2,i){
    obj2[i] = true;
    return obj2;
},obj2);

console.log('reduce',Date.now() - start);

start = Date.now();
arr.forEach(function(i){
    obj[i] = true;

});

console.log('forEach',Date.now() - start);

results are:

in node:
reduce 169
forEach 147

in node if you reverse the order:
forEach 170
reduce 145

in firefox:
reduce 956
forEach 1906

reversed in firefox:
forEach 2057
reduce 944

If this is for the browser, reduce seems twice as fast in firefox.  In node they appear equivalent.

forEach is about as concise as it gets, but hey, one line of code ain't bad. :)

Ted

On Oct 30, 2012, at 3:36 PM, Felipe Mobus <fmo...@gmail.com> wrote:

> You could use ES5's array.reduce() method, but it's gonna be a bit ugly

> [1,2,3,4,5,6,7,8].reduce(function(prev, cur) {
>  prev[cur] = (cur % 2) == 0;
>  return prev;
> }, {})

> On Tue, Oct 30, 2012 at 8:25 PM, mscdex <msc...@gmail.com> wrote:
>> On Oct 30, 5:50 pm, Felipe Gasper <fel...@felipegasper.com> wrote:
>>> Anything of the sort coming in JS, does anyone know? Maybe in some of
>>> the newer ES5 goodies?

>> Does this help?: https://github.com/joyent/node/wiki/ECMA-5-Mozilla-Features-Implement...

>> --
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> --
> Felipe Mobus
> http://fmobus.wait4.org

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