How to execute an arithmetic operation inside a string in Javascript?

Question

I have this little example:

var myoperation = "2+2";
var myoperation2="2*5/3";
var myoperation3="3+(4/2)"

is there anyway to execute this and get a result?

Thanks a lot in advance!

There's eval, or there's creating a script to parse the file manually. Which you use depends on how much effort you're willing to spend, and whether this is user input or not. — Qantas 94 Heavy
– Qantas 94 Heavy, Commented May 19, 2013 at 13:25
eval() seems to work just fine. However, unless it is used very judiciously and cautiously, it would really break your code. — Achrome
– Achrome, Commented May 19, 2013 at 13:26
eval will parse and execute whatever is in the string, but it's slow and can be dangerous. The only other option would be to parse the string and do the calculations yourself. — adeneo
– adeneo, Commented May 19, 2013 at 13:26

draxxxeus · Accepted Answer · 2013-05-19 13:24:04Z

3

You can use the eval() function. For eg: eval("2+2")

answered May 19, 2013 at 13:24

draxxxeus

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Comments

GriffLab · Accepted Answer · 2013-05-19 13:24:22Z

2

Use eval MDN: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/eval

Some people say it is evil, but it was designed for this exact purpose;

console.log(eval(myoperation)); // 4
console.log(eval(myoperation2)); // 3.33
console.log(eval(myoperation3)); // 5

answered May 19, 2013 at 13:24

GriffLab

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3 Comments

Havenard Over a year ago

It can run any JavaScript code inputted. I'd say PHP's eval() is dangerous, but in JavaScript... whats the worst that could happen?

Achrome Over a year ago

stackoverflow.com/questions/86513/…

Jason Over a year ago

Dont use eval, use (new Function(strCode))() , check out what Jay Garcia and the team at ModusCreate put out in the link above : moduscreate.com/javascript-performance-tips-tricks Why? performance.

xdazz · Accepted Answer · 2013-05-19 13:28:43Z

2

You could do this besides eval:

function run(myoperation) {
    return new Function('return ' + myoperation + ';').call();
}

run('2+2'); // return 4

answered May 19, 2013 at 13:28

xdazz

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Comments

Jordan Doyle · Accepted Answer · 2013-05-19 13:26:59Z

1

You can use eval for this.

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Don't pass any data from a remote server to eval before validating it. Damage can be done with eval.

answered May 19, 2013 at 13:26

Jordan Doyle

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Vivek Sadh · Accepted Answer · 2013-05-19 13:25:23Z

0

Pass the string to eval() function.

answered May 19, 2013 at 13:25

Vivek Sadh

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Comments

Anoop · Accepted Answer · 2013-05-19 13:27:13Z

0

you can use Function

var result = new Function("return " + "2+2")();

answered May 19, 2013 at 13:27

Anoop

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