Get deep property values from JavaScript objects by passing key path as an Array

JSUtilGetProp.js

const data = {
    foo: {
        bar: {
            cc: {
                str: "Hello I'm deep"
            },
            dd: "Just a level up",
        },
        dd: {
            cc: "Just another level up"
        }
    },
    bar: {
        dd: {
            foo: {
                str: "I'm foo string"
            }
        }
    }
};

Object.defineProperty(Object, "getProp", {
    writeable: false,
    configurable: false,
    enumerable: false,
    value: function getProp(collection, keyMap, ifNotMsg) {
        if (typeof collection !== "object") {
            return ifNotMsg || "Collection not valid";
        }

        if (typeof keyMap !== "object" || !Array.isArray(keyMap)) {
            return "Keymap not valid";
        }

        let tempResultObj;
        let firstKey = keyMap[0];
        let keyMapLength = keyMap.length;
        
        if(keyMapLength === 0 || firstKey === "") {
          return "Key map is empty";
        }

        if (!collection.hasOwnProperty(firstKey)) {
            return ifNotMsg;
        } else {
            tempResultObj = collection[firstKey];
            if (keyMapLength == 1) {
                return tempResultObj;
            }
        }
        for (let i = 1; i < keyMapLength; i++) {
            let currentKey = keyMap[i];

            if (typeof tempResultObj === "object" && tempResultObj.hasOwnProperty(currentKey)) {
                tempResultObj = tempResultObj[currentKey];
                if (i === keyMapLength - 1) {
                    return tempResultObj;
                }
            } else {
                return ifNotMsg;
            }
        }
    }
});

let tc1 = Object.getProp(data, ['foo', 'bar', 'cc', 'str'], 'Not available.');
let tc2 = Object.getProp(data, ['foo', 'cc', 'cc'], 'Not available.');
let tc3 = Object.getProp(data, ['foo', 'bar', 'dd'], 'Not available.');
let tc4 = Object.getProp(data, ['foo', 'bar'], 'Not available.');
let tc5 = Object.getProp(data, ['bar', 'foo'], 'Not available.');
let tc6 = Object.getProp(data, ['bar'], 'Not available.');

console.log("Test case: data, ['foo', 'bar', 'cc', 'str'] -->" + tc1);
console.log("Test case: data, ['foo', 'cc', 'cc'] -->" + tc2);
console.log("Test case: data, ['foo', 'bar', 'dd'] -->" + tc3);
console.log("Test case: data, ['foo', 'bar'] -->" + JSON.stringify(tc4));
console.log("Test case: data, ['bar', 'foo'] -->" + tc5);
console.log("Test case: data, ['bar'] -->" + tc6);

// Consol.log output
"Test case: data, ['foo', 'bar', 'cc', 'str'] -->Hello I'm deep"
"Test case: data, ['foo', 'cc', 'cc'] -->Not available."
"Test case: data, ['foo', 'bar', 'dd'] -->Just a level up"
"Test case: data, ['foo', 'bar'] -->{\"cc\":{\"str\":\"Hello I'm deep\"},\"dd\":\"Just a level up\"}"
"Test case: data, ['bar', 'foo'] -->Not available."
"Test case: data, ['bar'] -->[object Object]"

Let me know if there are any other test cases that you want to cover.