Set a value of property at any deeply nested JavaScript object collection and return the newly created object

JSUtilSetProp.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, "setProp", {
    writeable: false,
    configurable: false,
    enumerable: false,
    value: function setProp(collection, keyMap, value) {
        if (typeof collection !== "object") {
            return "Collection is not valid";
        }

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

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

        let _newCollection = JSON.parse(JSON.stringify(collection));
      
        if (keyMapLength == 1) {
            _newCollection[firstKey] = value;
            return _newCollection;
        }
                      
        
        if (!_newCollection.hasOwnProperty(firstKey)) {
            return "Key not found.";
        } else {
            tempResultObj = _newCollection[firstKey];
        }
      
        for (let i = 1; i < keyMapLength; i++) {
            let currentKey = keyMap[i];

            if (typeof tempResultObj === "object" && 
                tempResultObj.hasOwnProperty(currentKey)) {
                if (i === keyMapLength - 1) {
                  tempResultObj[currentKey] = value;
                  return _newCollection;
                } else {
                  tempResultObj = tempResultObj[currentKey];
                }
            } else {
                return "Key not found";
            }
        }
    }
});



let tc1 = Object.setProp(data, ['foo', 'bar', 'cc', 'str'], 'This is a new string');
let tc2 = Object.setProp(data, ['foo', 'bar','cc'], [25,25,60]);
let tc3 = Object.setProp(data, ['foo', 'bar', 'dd'], "Test string");
let tc4 = Object.setProp(data, ['foo', 'bar'], {"fizz": "Fizz fizz", "fuzz": "Fuzz fuzz"});
let tc5 = Object.setProp(data, ['bar', 'foo'], new Date());
let tc6 = Object.setProp(data, ['bar'], "Hello");
let tc7 = Object.setProp(data, ['tt'], "Hello");
let tc8 = Object.setProp(data, [''], new Date());

console.log("Test case: data, ['foo', 'bar', 'cc', 'str'] -->" + JSON.stringify(tc1));
console.log("Test case: data, ['foo', 'bar', 'cc'] -->" + JSON.stringify(tc2));
console.log("Test case: data, ['foo', 'bar', 'dd'] -->" + JSON.stringify(tc3));
console.log("Test case: data, ['foo', 'bar'] -->" + JSON.stringify(tc4));
console.log("Test case: data, ['bar', 'foo'] -->" + JSON.stringify(tc5));
console.log("Test case: data, ['bar'] -->" + JSON.stringify(tc6));
console.log("Test case: data, ['tt'], 'Hello' -->" + JSON.stringify(tc7));
console.log("Test case: data, [''], 'Hello' -->" + JSON.stringify(tc8));

//Console.log output
"Test case: data, ['foo', 'bar', 'cc', 'str'] -->{\"foo\":{\"bar\":{\"cc\":{\"str\":\"This is a new string\"},\"dd\":\"Just a level up\"},\"dd\":{\"cc\":\"Just another level up\"}},\"bar\":{\"dd\":{\"foo\":{\"str\":\"I'm foo string\"}}}}"
"Test case: data, ['foo', 'bar', 'cc'] -->{\"foo\":{\"bar\":{\"cc\":[25,25,60],\"dd\":\"Just a level up\"},\"dd\":{\"cc\":\"Just another level up\"}},\"bar\":{\"dd\":{\"foo\":{\"str\":\"I'm foo string\"}}}}"
"Test case: data, ['foo', 'bar', 'dd'] -->{\"foo\":{\"bar\":{\"cc\":{\"str\":\"Hello I'm deep\"},\"dd\":\"Test string\"},\"dd\":{\"cc\":\"Just another level up\"}},\"bar\":{\"dd\":{\"foo\":{\"str\":\"I'm foo string\"}}}}"
"Test case: data, ['foo', 'bar'] -->{\"foo\":{\"bar\":{\"fizz\":\"Fizz fizz\",\"fuzz\":\"Fuzz fuzz\"},\"dd\":{\"cc\":\"Just another level up\"}},\"bar\":{\"dd\":{\"foo\":{\"str\":\"I'm foo string\"}}}}"
"Test case: data, ['bar', 'foo'] -->\"Key not found\""
"Test case: data, ['bar'] -->{\"foo\":{\"bar\":{\"cc\":{\"str\":\"Hello I'm deep\"},\"dd\":\"Just a level up\"},\"dd\":{\"cc\":\"Just another level up\"}},\"bar\":\"Hello\"}"
"Test case: data, ['tt'], 'Hello' -->{\"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\"}}},\"tt\":\"Hello\"}"
"Test case: data, [''], 'Hello' -->\"Key map is empty\""