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, May 19 '13 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, May 19 '13 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, May 19 '13 at 13:26

score 3 · Answer 1 · answered May 19 '13 at 13:24

3

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

answered May 19 '13 at 13:24

draxxxeus

score 2 · Accepted Answer · answered May 19 '13 at 13:24

2

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 '13 at 13:24

GriffLab

It can run any JavaScript code inputted. I'd say PHP's `eval()` is dangerous, but in JavaScript... whats the worst that could happen? – Havenard May 19 '13 at 13:27
2

http://stackoverflow.com/questions/86513/why-is-using-the-javascript-eval-function-a-bad-idea – Achrome May 19 '13 at 13:27
1

Dont use eval, use (new Function(strCode))() , check out what Jay Garcia and the team at ModusCreate put out in the link above : http://moduscreate.com/javascript-performance-tips-tricks/ Why? performance. – Jason May 19 '13 at 13:44

score 1 · Answer 3 · answered May 19 '13 at 13:26

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 '13 at 13:26

Jordan Doyle

score 1 · Answer 4 · answered May 19 '13 at 13:28

1

You could do this besides eval:

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

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

answered May 19 '13 at 13:28

xdazz

score 0 · Answer 5 · answered May 19 '13 at 13:25

0

Pass the string to eval() function.

answered May 19 '13 at 13:25

Vivek Sadh

score 0 · Answer 6 · answered May 19 '13 at 13:27

0

you can use Function

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

answered May 19 '13 at 13:27

Anoop

6 Answers6