how to evaluate this Number("2/4") in JavaScript

Question

Hey guys i want to extract/evaluate the answer 2/4 in a string even ehen doing Number ("2/4") it gives me NaN as a result which is fairly reasonable! So my question is how can i evaluate this fraction from a string?

Dude!! Seriously extremely thanks for that quick reply!!! So, can i use this to change the result obtained from regexp? I guss i can.. — Mrityunjay Bhardwaj, Dec 10 '15 at 06:23
@Tushar this does not work. It parses only the first part of the string. `parseFloat("5/4")` returns 5. — Ortiga, Dec 10 '15 at 06:23

score 3 · Answer 1 · edited Dec 10 '15 at 06:36

3

You can do eval("2/4"), which will properly result in 0.5.
However, using eval is a really bad idea...

If you always have a fraction in format A/B, you can split it up and compute:

var s = "11/47";
var ssplit = s.split('/');

document.body.innerText = ssplit[0] / ssplit[1];

Note that Division operator / will implicitly cast strings "11" and "47" to 11 and 47 Numbers.

edited Dec 10 '15 at 06:36

Tushar

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answered Dec 10 '15 at 06:26

Yeldar Kurmangaliyev

33,467
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Don't need to cast, `/` will cast it implicitly `ssplit[0] / ssplit[1]` – Tushar Dec 10 '15 at 06:29
@Tushar Thank you! :) – Yeldar Kurmangaliyev Dec 10 '15 at 06:29

score 2 · Answer 2 · answered Dec 10 '15 at 06:26

2

You are looking for eval. Note

parseFloat("2/4")
2
parseFloat("4/2")
4
eval("4/2")
2
eval("2/4")
0.5

answered Dec 10 '15 at 06:26

dnit13

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score 1 · Answer 3 · answered Dec 10 '15 at 06:27

1

 function myFunction() {
       var str = "3/4";
     var res = str.split("/");
    alert(parseFloat(res[0]/res[1]));
 }

answered Dec 10 '15 at 06:27

solanki dev

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8

score 0 · Answer 4 · answered Dec 10 '15 at 06:26

0

Try with eval function :

eval("2/4");

answered Dec 10 '15 at 06:26

Tᴀʀᴇǫ Mᴀʜᴍᴏᴏᴅ

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Ortiga · Answer 5 · 2015-12-10T06:31:27.030

0

(function(str){
    var numbers = str.split("/").map(Number);
    return numbers[0] / numbers[1]; 
})("2/4")

Keep in mind this does not check for invalid input.

edited Dec 10 '15 at 06:31

answered Dec 10 '15 at 06:28

Ortiga

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1

Why not `map(Number)`? – Dec 10 '15 at 06:30
@torazaburo You're right, changed – Ortiga Dec 10 '15 at 06:31

score 0 · Answer 6 · answered Dec 10 '15 at 06:29

Parsing the string only valid for numbers like 0-10 and a decimal (.) and all other if included will then result in NaN.

So, what you can do is like this:

Number(2/4)//0.5
parseFloat(2/4)//0.5
Number('2')/Number('4');//0.5
parseFloat('2')/parseFloat('4');//0.5
Number('2/4');//NaN as / is not parsable string for number
parseFloat('2/4');//2 as upto valid parsable string
parseFloat('1234/4');//1234

So, you can split string then use that like @Yeldar Kurmangaliyev answered for you.

how to evaluate this Number("2/4") in JavaScript

6 Answers6