javascript ignore-if-null operator?

Question

In javascript I have a lot of code like this.

if (ctrl && ctrl.main && ctrl.main.user) {
    SetTheme(ctrl.main.user.theme);
}

which is annoyingly long. In other, languages you can do simply

SetTheme(ctrl?.main?.user?.theme);

Is there any way to do that in javascript?

I tried,

function safeGet(a,b) { return a ? a[b] : null; }

and

SetTheme(safeGet(safeGet(safeGet(ctrl, 'main'), 'user'), 'theme'));

But that's not very readable.

Answer 1

The correct short cut could be

if (((ctrl || {}).main || {}).user) { // ...

Or you could use an array as path, or a dot separated string as path and check aginst existence and return the value.

function getValue(object, path) {
    return path.split('.').reduce(function (o, k) {
        return (o || {})[k];
    }, object);
}

var ctrl = { main: { user: { theme: 42 } } };

console.log(getValue(ctrl, "main.user.theme"));