Find Property in Nested Object

findPropertyInNestedObject.ts

const originalObject = {
    foo: {},
    bar: "BAR",
    baz: {
        a: {},
        b: {},
        c: {
            d: "DDD",
            e: "EEE",
            f: "FFF",
            g: "GGG",
            h: "HHH",
            i: "III",
            j: "JJJ",
            k: "KKK",
            l: "LLL",
            m: "MMM",
            n: "NNN",
            o: "OOO",
            p: "PPP",
        }
    },
}

function findValueOfPropertyInNestedObject(obj: Object, propertyName: string) {
    for (var prop in obj) {
        if (Object.prototype.hasOwnProperty.call(obj, prop)) {
            const valueOfProperty = obj[prop];
            const valueOfPropertyIsObject = typeof valueOfProperty === "object";
            const propertyFound = prop === propertyName;
            
            if (propertyFound) {
                return valueOfProperty;
            }

            if (valueOfPropertyIsObject) {
                const childValue = findValueOfPropertyInNestedObject(valueOfProperty, propertyName);
                
                if (childValue) {
                    return childValue;
                }
            }
        }
    }

    return undefined;
}

const p = findValueOfPropertyInNestedObject(originalObject, "p");

console.log(p);

Hi! I came here via your blog post: https://topherpedersen.blog/2024/05/09/javascript-for-loop-over-properties-in-an-object/

Watch out: also true for null!

const valueOfPropertyIsObject = typeof valueOfProperty === "object";

This condition does not return falsy child values such as 0, false and "":

if (childValue) {

To catch such issues, you can write unit tests where properties have values such as null, false and 0.

Object.entries() is now quite well supported – e.g.:

for (const [key, value] of Object.entries(myObj)) {
  // ···
}