Make a string call a function in JS

Question

I want this to work:

I have defined a function:

function callback_1() {
 // Do something
}

I have a callback string that defines a callback:

var functionString = 'callback_' + 1 + '()';

I want to make that string actually call the function callback_1 How do I do that?

Will eval be sandboxed? I mean can I the defined function be outside eval context? — einstein
– einstein, Commented Sep 21, 2012 at 11:49
have a look at eval, but then try to figure out how you don't need it — sra
– sra, Commented Sep 21, 2012 at 11:49
NOO "eval()" is EVIL, the only time you had (not have, had) to use it was when parsing JSON back in the days. I've not seen any situation where eval was the only solution since... — Elias Van Ootegem
– Elias Van Ootegem, Commented Sep 21, 2012 at 12:03

Denys Séguret · Accepted Answer · 2012-09-21 11:59:37Z

6

As your functionString is in fact mainly a function's name, you can do that

window['callback_' + 1]();

This is much secure than eval as it only executes a function you yet have.

If you want to use the functionString you have (with its "()" at the end), you can use

window[functionString.slice(0, -2)]();

edited Sep 21, 2012 at 11:59

answered Sep 21, 2012 at 11:49

Denys Séguret

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1 Comment

einstein Over a year ago

Tried this and it works. Though in the string we need to remove ().

Aravindhan · Accepted Answer · 2012-09-21 11:49:18Z

0

Try this: it is working for me

        eval(functionString);

answered Sep 21, 2012 at 11:49

Aravindhan

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5 Comments

einstein Over a year ago

Will eval be sandboxed? I mean can the defined function be outside eval context?

Vlad Balmos Over a year ago

remember that in most cases, eval is evil :). dystroy answer is the one to go

qwertymk Over a year ago

@VladBalmos theres no reason this answer should be downvoted. If you like one answer over another then vote up the one you like.

Elias Van Ootegem Over a year ago

@qwertymk: in this case, the answer can produce potentially harmful code, if the eval-string is based on user input or an ajax response. potentially dangerous code is a valid reason for down-voting, says the FAQ

Vlad Balmos Over a year ago

@qwertymk what makes you think I down voted? Regardless, I am entitled to up / down vote based on the quality of the answer. See Elias comment on why it may be down voted

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