Can Javascript get a function as text? I'm thinking like the inverse of eval().
function derp() { a(); b(); c(); }
alert(derp.asString());
The result would be something like
"a(); b(); c();"
Does it exist?
-
It's possible to convert a JavaScript function to text, and it's also possible to convert the text back into a function.Anderson Green– Anderson Green2013-04-26 22:06:40 +00:00Commented Apr 26, 2013 at 22:06
Add a comment
|
2 Answers
Updated to include caveats in the comments below from CMS, Tim Down, MooGoo:
The closest thing available to what you're after is calling .toString() on a function to get the full function text, like this:
function derp() { a(); b(); c(); }
alert(derp.toString()); //"function derp() { a(); b(); c(); }"
You can give it a try here, some caveats to be aware of though:
- The
.toString()on function is implementation-dependent (Spec here section 15.3.4.2)- From the spec: An implementation-dependent representation of the function is returned. This representation has the syntax of a FunctionDeclaration. Note in particular that the use and placement of white space, line terminators, and semicolons within the representation string is implementation-dependent.
- Noted differences in Opera Mobile, early Safari, neither displaying source like my example above.
- Firefox returns a compiled function, after optimization, for example:
(function() { x=5; 1+2+3; }).toString()==function() { x=5; }
12 Comments
Nick Craver
@delnan - Various objects override the
object.toString() method, in the case of functions you get the full function text :)
Tim Down
name is non-standard and isn't supported in all browsers. Notable non-supporters include (would you believe) IE.
Christian C. Salvadó
@Nick, This will work on almost all browsers, but maybe is worth mentioning that the
Function.prototype.toString method returns an "implementation-dependent representation of the function", and in some implementations (Opera Mobile and Older Safari versions IIRC) it will not return the source code of the function, also the name property on function objects is non-standard.Christian C. Salvadó
@Nick, yes but I think the specification should be more formal, in almost all implementations, the spec. then is not strictly followed, for example, an anonymous
FunctionExpression, like (function() {}).toString() returns a string that does not represent the grammar of a FunctionDeclaration: "function () {}", the mandatory Identifier token is missing... BTW I've found the issues where Opera Mobile made PrototypeJS and jQuery fail. |
function derp() { a(); b(); c(); }
alert(derp.toString());
