Run a Javascript function stored in a string variable

Question

I have got the following function coming from an ajax call which is stored in a string variable.

obj.action="DisplayActivity('modalDisplay', 0, 4);"

I am trying to run it but without success. I tried with:

eval(obj.action);

and with:

window[obj.action]

Any ideas? Thanks.

• ibrahim mahrir: For that eval to work, DisplayActivity should be defined somewhere.
• Jack Bashford: Does DisplayActivity actually exist? You may be getting some errors in your console if it doesn't.
• Taplar: jsfiddle.net/Lov981gy works fine.
• Felix Kling: eval works, of course only if the function you are trying to call is in scope. window[obj.action] makes no sense.
• D.B: yes, for sure. the function is already defined. I can run it just calling like that DisplayActivity('modalDisplay', 0, 4); in the same code section. but i need to invoke it from the variable cos it is coming from the server side.

Answer 1

Try using New Function:

let s = "console.log('Hello '+a)",
call = new Function('a', s)
call('world!')

Make sure to avoid to call stuffs from a GET/POST or this will lead to be a typical xss, allowing to change your DOM from a special crafted link.

Answer 2

I suppose it's a scoping problem.

Try:

eval("global.tmp = function(DisplayActivity){" + obj.action + "};");
global.tmp(DisplayActivity);