How fast is parseFloat Vs. float ints in JavaScript?

Question

I'm getting a huge dataset from a client's internal API. It'll contain a bunch of numerical data of prices such as: $31.23. He gives them to me as {"spend":"21.23"} which is fine, but I was concerned that after 1000+ items and running parseFloat() on all of those values (on top of graphing them) might be resource heavy on the client's browser.

Has anyone done this?

==Update==

I'm sorry. My question was too vague. My concern was that it's a string and i'm parsing it. My issue was is parseFloat faster than just an int. I.e. is appending parseFloat("12.12") to a div faster than simply just appending 12.12 and if so, how much faster.

Profile it! Make a 1,000 parseFloat calls and time it. Than 100,000. — Emil Ivanov
– Emil Ivanov, Commented Jul 18, 2011 at 18:24
@Oscar: You say "just an int" but then you say 12.12; which is it? Do you mean parsing the string "12.12" (to 12) or skipping parsing altogether? — Dan Tao
– Dan Tao, Commented Jul 18, 2011 at 23:28

Dan Tao · Accepted Answer · 2011-07-18 18:55:13Z

7

On my work machine (Mac OS X, Intel 2 GHz Core i7), I saw the following results on jsperf.com:

Browser    | parseFloat calls per second
----------------------------------------
Chrome 12  | 5.3 million
Firefox 6  | 21.7 million
IE 8       | 666.9 thousand <- totally unfair, ran on virtual machine
Opera 11   | 5.2 million

This is far from an exhaustive survey; but at a rough minimum of over 600 thousand calls per second (and that on a virtual machine), I think you should be good.

edited Jul 18, 2011 at 18:55

answered Jul 18, 2011 at 18:49

Dan Tao

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1 Comment

Oscar Godson Over a year ago

Cool, thanks. That answers my question by far the best. My concern though was is doing something with parseFloat faster than doing something with just a raw int like 12.12 rather than parseFloat("12.12"). see my updated question. Either way, this is 600k calls per second, so it should be fine. Thanks!

SoEzPz · Accepted Answer · 2015-07-18 00:22:17Z

2

In regard for speed of parseFloat or parseInt MDN recommends using the unary operator + instead, as in

+"12.12"
=> 12.12

MDN Link

The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number.

answered Jul 18, 2015 at 0:22

SoEzPz

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ghiscoding Over a year ago

The only side effect of using the + instead of parseFloat is that it won't work on a string that has a number at the beginning with text as suffix, for example +"22blah" result as NaN while parseFloat(22blah) result as 22... and BTW I just tested it because I wasn't sure of the output and I would have preferred to use + but in my use I can't because of this side effect

Mihai Iorga · Accepted Answer · 2011-07-18 18:26:36Z

0

you know that parseFloat() is based on the browser. So as far as I know the browser could crash after 200 values, could work just fine after 10.000 value.

It depends on how many tabs that browser has, what other scripts is running, how much CPU is free for processing, and of course what browser

if your client uses firefox with 1000 addons it will never run your script smoothly.

just my opinion. If you want to do it nice you should preprocess on a server then display.

answered Jul 18, 2011 at 18:26

Mihai Iorga

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Oscar Godson Over a year ago

Of course it's based on the browser as all JS is based on the browser. My concern was is it faster to process just ints like 12.12 or parseFloat("12.12") and if there was a difference between it.

Not a Name · Accepted Answer · 2011-07-18 18:50:41Z

0

Type

javascript:a = +new Date; x = 100000; while (--x) parseFloat("21.23"); alert(+new Date - a);

Into your url bar.

This is the only way to know for sure.

In honesty, you can't answer the question. It depends on the browser, for example, firefox 8 should be faster than 6, and so on.

answered Jul 18, 2011 at 18:50

Not a Name

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