Javascript notification when accessing an undefined object property

Question

I think Javascript is trying to kill me. Errors that would be caught by a compiler in any statically-typed language including FORTRAN, or turn into a run-time exception in any decent dynamically-typed language are swallowed silently by Javascript, patiently waiting to manifest as a bug elsewhere.

Whenever we write Frontend code (nowadays with Angular), we spend most of our time hunting down mistakes such as writing $scope.result = data.results instead of data.result . While some tools help, it still requires an astonishing amount of work.

Is there a way to cause the Javascript environment (in a browser) to log a warning whenever someone tries to read a non-existing object property? I don't want to change the language's semantics - accessing data.results should still returned undefined , I just want to see a warning on the console saying "Non-existing property accessed, file ... line ...".

Answer 1

This is a duplicate of this question I think : Force JavaScript exception/error when reading an undefined object property?

In short : no satisfying solution for your use case, but if you all use firefox you can use javascript.options.strict set to true to have warning in such cases :)

Answer 2

In ECMAScript 2015 you can use Proxy to do this, for example:

function createObject(obj) {
    const handler = {
        get: function(target, name){
            if (name in target) {
                return target[name];
            } else {
                console.warn("accessing undefined object property: " + name);
                return undefined;
            }
        }
    };
    return new Proxy(obj, handler);
}


let a = createObject({
    b: 1,
    c: undefined
});

a.b;
a.c;
a.d; // accessing not existing object property: d

Answer 3

This might seem amateurish, but you might be able to store all of your variables in a loop able object like an array or object and then loop through them to check if any of them are undefined , then print the results of that. You might be able to use a dictionary with key:value pairs. Not ideal, though.