Convert a string (used to be function) to Javascript Function

Question

I would like to convert a function that is a string now to Function.

This returns an error, any suggestions?

var a = 'function () { return "a"; }'.trim();

console.log(a);

var b = eval(a);

Please tell us about the real problem you're trying to solve. — Denys Séguret
– Denys Séguret, Commented Dec 29, 2015 at 14:42

Denys Séguret · Accepted Answer · 2015-12-29 14:54:27Z

2

A "solution" would be to add parenthesis around the string, in order to evaluate an expression :

var a = 'function () { return "a"; }'.trim();

console.log(a);

var b = eval('('+a+')');

But it's clear you're after a bad design. There's no problem that should be solved that way.

Note that it's marginally more secure to use the Function constructor (which has no access to local variables) than to use eval:

var fun = new Function('return "a";')

edited Dec 29, 2015 at 14:54

answered Dec 29, 2015 at 14:42

Denys Séguret

384k90 gold badges813 silver badges780 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

puppeteer701 Over a year ago

I need to save function in a mongodb, any suggestions?

Xotic750 Over a year ago

need? Why? Perhaps you could explain what you are trying to do.

Denys Séguret Over a year ago

Why would you need to save a function ? This will be very slow and will lead to bugs and of course security problems if you're taking user inputs to do so. You should rather model the problem and define a structure enabling the reproduction of the behavior. See also stackoverflow.com/questions/197769/…

puppeteer701 Over a year ago

the function is a callback and it can be different on every entry.

Collectives™ on Stack Overflow

Convert a string (used to be function) to Javascript Function

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related