Calling a JavaScript functions whose name is saved in a string

Question

Is it possible to run a function whose name is saved in a string?

For example: I have three functions:

function nr1(p0, p1){
    /* [...] */
}
function nr2(p0, p1){
    /* [...] */
}
function nr3(p0, p1){
    /* [...] */
}

and I have a string whose content is a function name, for example:

var a_string = "nr2(27, 42)";

Is it possible to execute the function whose name is stored in the string?

if you know the parent object (e.g. window) then you can do e.g. window['foo']() — CrayonViolent
– CrayonViolent, Commented Aug 3, 2016 at 2:20
have you tried using eval ? try eval(a_string); note eval is bad.. you should change your implementation — Jairo Malanay
– Jairo Malanay, Commented Aug 3, 2016 at 2:20
Possible? Maybe. A reasonable solution to anything? Almost never. — Alexander O'Mara
– Alexander O'Mara, Commented Aug 3, 2016 at 2:21
Possible duplicate of How to execute a JavaScript function when I have its name as a string — jon_athan_hall
– jon_athan_hall, Commented Aug 3, 2016 at 2:26

scniro · Accepted Answer · 2016-08-03 02:30:27Z

1

you can eval() it. Observe the following example...

function something() {
    console.log('did');
} 

var str = 'something()'

eval(str) // did

As comments suggest, not the best idea to take and run with - though it works... To expand on that just a bit more, I found this blog post which shares some good pointers on the somewhat controversial usage of this technique: eval() isn’t evil, just misunderstood

JSFiddle - simple demo

edited Aug 3, 2016 at 2:30

answered Aug 3, 2016 at 2:24

scniro

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2 Comments

scniro Over a year ago

@EisregenGruss36 you are most welcome! I also included a link to a blog post I felt was pretty interesting which should answer anything you'd like to know about eval

niklassc Over a year ago

Thanks for your response. I tried it and it works. I'm aware that it is probably not the best way to do it but I don't know how else I could do it. I am using it in Electron to send a String from the renderer process to the main process, in order to be able to execute main-process-functions from the renderer process.

Community · Accepted Answer · 2017-05-23 12:08:03Z

1

you can use eval to evaluates JavaScript code represented as a string. eval(a_string) but

eval is bad

Improper use of eval opens up your code for injection attacks
Debugging can be more challenging (no line numbers, etc.)
eval'd code executes more slowly (no opportunity to compile/cache eval'd code)

you better change your implementation instead of saving a string function call

function nr1(p0, p1){
    console.log('nr1 p0: ', p0);
    console.log('nr1 p1: ', p1);
}

function nr2(p0, p1){
    console.log('nr2 p0: ', p0);
    console.log('nr2 p1: ', p1);
}

function nr3(p0, p1){
    console.log('nr3 p0: ', p0);
    console.log('nr3 p1: ', p1);
}

var a_string = "nr2(27, 42)";

eval(a_string);

edited May 23, 2017 at 12:08

CommunityBot

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answered Aug 3, 2016 at 2:32

Jairo Malanay

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Comments

Andrew Li · Accepted Answer · 2016-08-03 02:39:03Z

1

You can do eval, although it is frowned upon because of it's vulnerabilities. Something you could do is find it in the window object and then execute:

window["functionName"](args);

Calling with eval:

function test() { 
    console.log('test');
}

var fnstring = "test()";
eval(fnstring);

edited Aug 3, 2016 at 2:39

answered Aug 3, 2016 at 2:25

Andrew Li

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