Is it possible to get the instanceof operator result as a value?

Question

Let's say I have a variable that could represent a number of different models (Objects). I want to respond to each differently, ideally through a switch statement. Is it possible to get the instanceof result as a value?

For example, something like this:

function determineModel(model) {
    switch (model instanceof) {  // this does not work
        case 'Foo':
            // do something
            break;
        case 'Bar':
            // do something else
            break;
        default:
    }
}

how about `model.constructor`? That gives you a reference to the constructor function — Pointy, Mar 12 '19 at 23:28
This might give you what you want: https://stackoverflow.com/a/10314492/4126658 — Benjamin Parnell, Mar 12 '19 at 23:29

score 1 · Answer 1 · answered Mar 12 '19 at 23:29

1

You can use model.constructor.name:

switch (model.constructor.name) {
    case "Foo":
        //Do something
    case "Bar":
        //Do something
    default:
        //Default something
}

answered Mar 12 '19 at 23:29

Jack Bashford

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Jonathan Gray · Answer 2 · 2019-03-12T23:41:08.903

Something like this should work:

function determineModel(model) {
    switch(model.constructor) {
        case SomeObject:
            console.log('Constructor is SomeObject');
            break;
        case OtherObject:
            console.log('Constructor is OtherObject');
            break;
        default:
            console.log('Constructor is ' + model.constructor.name);
        }
    }

determineModel(new OtherObject());

Roko C. Buljan · Answer 3 · 2019-04-14T23:40:16.833

0

You could go for model.constructor.name and even without the switch statement:

function determineModel(model) {
    return {
      Foo: someFnFoo,
      Bar: someFnBar,
    }[model.constructor.name](); // Execute someFn* given the Object's constr. name
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor

edited Apr 14 '19 at 23:40

answered Mar 12 '19 at 23:30

Roko C. Buljan

196,159
39
305
313

Is it possible to get the instanceof operator result as a value?

3 Answers3