function someFunc() { return 'Hello, world'; }
function call(funcName) { eval(funcName + '()'); }
console.log(call('someFunc'));
But console.log doesn't print 'Hello world'. How can I return value after eval function?
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Max Frai
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3 Answers
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You want:
call(funcName) { window[funcName](); }
And don't use the void keyword. It ignores return values and always returns undefined from a statement.
Raynos
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I'm not too sure about this, but if eval works in with clousures (like functions in functions etc), than that code won't work. – Alxandr Mar 06 '11 at 14:06
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@Alxandr depends where the call function is defined. Depends where `someFunc` is defined. It's bad to rely on that. You really want to store functions on an object and call them by string key on the object. – Raynos Mar 06 '11 at 14:07
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@Raynos how about something like `(this[fnName] || window[fnName])()`? – Alxandr Mar 06 '11 at 14:11
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However, what if I did `function a() { var b = function() {/*do something*/}; call('b'); }` (silly example, yes I know). Not that it has anything to do with OP, but I'm just curious :-P – Alxandr Mar 06 '11 at 14:12
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@Alxandr `b` is defined as a local variable on the stack. It is not accesible in `this` not in the global scope (`window`). `b`lives in the CallObject. [You can't programmatically access it](http://stackoverflow.com/questions/3831932/access-all-local-variables) – Raynos Mar 06 '11 at 14:18
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@Raynos what would `eval('b')` yield when called inside a then? I've tried this in FF now, and it gives me the function b, thought it might differ between browsers. So, how about something like `function call(name) { var f = eval(name); if(typeof name == 'function') { f(); }}`. Then you just need to do some sort of regex to check that name isn't malicious js. A bit overkill maybe, but that use of eval I wouldn't call evil, no? – Alxandr Mar 06 '11 at 14:22
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@Alxandr alternatively don't write shit generic code that requires the use of `eval`. Sorry but eval should be avoided for most cases. It's uses are very limited. – Raynos Mar 06 '11 at 15:06
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To answer your question using eval :
function someFunc() { return 'Hello, world'; }
function call(funcName) { return eval(funcName + '()'); }
console.log(call('someFunc'));
And you can use eval if you trust the input. this is the rule of thumb
Royi Namir
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Don't use eval -- it's evil. Why don't you try this:
Get JavaScript function-object from its name as a string?
After getting a reference to the function, you can simply call it and use the return value directly.
