Javascript returns only one timestamp inside for loop

Question

I want to generate a timestamp for each item inside the for loop but i am getting only one timestamp inside the loop.How can i make new timestamp for each item in the for loop in javascript.

for (var i = 0 ; i < 5; i++ ) { vm.workers[i].id = (new Date()).getTime(); }

This one provides only one timestamp instead of 5 different timestamp can anyone tell me how to generate multiple timestamps inside the loop.

You get the same number because the loop happens so fast they each have the same value.... — epascarello, Dec 04 '17 at 14:06
@epascarello so how can i have different timestamps inside the loop itself — Nidhin Kumar, Dec 04 '17 at 14:07
They're all the same value due to the speed of the loop. `console.time(); for (var i = 0 ; i < 5; i++ ) { console.log(new Date().getTime()); }; console.timeEnd();` — subhaze, Dec 04 '17 at 14:08
https://stackoverflow.com/questions/105034/create-guid-uuid-in-javascript — Nope, Dec 04 '17 at 14:11
I've retracted both my close vote and my down vote since it's a valid question that I'm sure another JS newbie will stumble upon. — nicholaswmin, Dec 04 '17 at 14:19

score 7 · Accepted Answer · answered Dec 04 '17 at 14:09

7

All the ids are the same because the loop takes no time at all to run. So how can you generate a unique number for each? Add one each time you use it.

var ts = (new Date()).getTime();
for (var i = 0 ; i < 5; i++ ) { 
  vm.workers[i].id = ts++
}

answered Dec 04 '17 at 14:09

epascarello

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score 2 · Answer 2 · edited Dec 04 '17 at 14:55

2

Answering the original question which had this loop:

for (var i = 0 ; i < 5; i++ ) { new Date().getTime(); }

You're not doing anything with them so it will only print the last one or none at all if you're not using the console.

Try logging each one with console.log.

for (var i = 0 ; i < 5; i++ ) { console.log(new Date().getTime()); }

assign them to a an array and add them like so like so will give you an array of date/time stanmps:

var list = [];
for (var i = 0 ; i < 5; i++ ) { list.push(new Date().getTime()); }
console.log(list);

edited Dec 04 '17 at 14:55

mplungjan

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answered Dec 04 '17 at 14:09

DeadEnglish

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please try your code in you browser first; at least with a computer manufactured after 2010 :) – InQβ Dec 04 '17 at 14:12
@no1xsyzy It seems to work in chrome dev tools https://i.imgur.com/u21dRat.png :) – DeadEnglish Dec 04 '17 at 14:15
that is just by accident; the loop ran from one millisecond to next one, which not *must* but *may* produce different timestamps, and in this best result, it still produces only two timestamps – InQβ Dec 04 '17 at 14:19
@no1xsyzy, Not really. It's pushing to the array every loop so a new timestamp is generated (even though it is identical). When I answered, OP didn't specify they needed to be distinct timestamps, just that there needed to be 5 instead of 1. – DeadEnglish Dec 04 '17 at 14:27
That makes sense now; not noticed the time. – InQβ Dec 04 '17 at 14:42

nicholaswmin · Answer 3 · 2017-12-04T14:10:56.647

0

A simple loop iteration can certainly take less than a millisecond to complete, hence you're getting the same timestamp.

Find a more reliable way to create id's such as a GUID.

Here's a function, taken from this S.O answer that creates GUID's:

function guid() {
  function s4() {
    return Math.floor((1 + Math.random()) * 0x10000)
      .toString(16)
      .substring(1);
  }
  return s4() + s4() + '-' + s4() + '-' + s4() + '-' +
    s4() + '-' + s4() + s4() + s4();
}

console.log(guid())

edited Dec 04 '17 at 14:10

answered Dec 04 '17 at 14:04

nicholaswmin

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the question is not that all 5 timestamps are the same, but that there is only 1 timestamp – Aleksey Solovey Dec 04 '17 at 14:06
2

I'm pretty sure his problem is what I answered, he's just explaining it badly – nicholaswmin Dec 04 '17 at 14:07
Or maybe the answer is right and the people are assuming the wrong thing. +1 since it is how I read the question. – epascarello Dec 04 '17 at 14:07
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@AlekseySolovey that was the original question before OP posted more code making it an XY Problem – charlietfl Dec 04 '17 at 14:07
@charlietfl I've explained what the problem is - I'm not gonna spoon-feed to the OP what a GUID is. – nicholaswmin Dec 04 '17 at 14:11
@charlietfl Even if I didn't, your comment wasn't really a good fit. A GUID is a general term that can be googled if my link gets broken. Don't be pedantic. – nicholaswmin Dec 04 '17 at 14:15

Javascript returns only one timestamp inside for loop

3 Answers3