Find the number of undefined properties in an object with Lodash

Question

let x =    {
      "name": undefined,
      "value": "tr",
      "prop1": undefined,
      "prop2": "test",
      "prop3": 123
    };

I need to find the number of properties that are undefined, so in this case 2.

Answer 1

With regular JS:

Good comments pointed out that we can indeed immediately filter; more efficient:

Object.values(x).filter(v=> v === undefined).length

---

With Lodash

_.filter(x, (v, k) => v === undefined).length