How To Write This JavaScript Code Without Eval?

How to write this JavaScript code without eval? var typeOfString = eval('typeof ' + that.modules[modName].varName); if (typeOfString !== 'undefined') { doSomething(); } The poin

Solution 1:

in JS every variable is a property, if you have no idea whose property it is, it's a window property, so I suppose, in your case, this could work:

var typeOFString = typeof window[that.modules[modName].varName]
if (typeOFString !== "undefined") {
  doSomething();
}

Solution 2:

Since you are only testing for the existence of the item, you can use in rather than typeof.

So for global variables as per ZJR's answer, you can look for them on the window object:

if (that.modules[modName].varName in window) {
    ...
}

If you need to look for local variables there's no way to do that without eval. But this would be a sign of a serious misdesign further up the line.