Profile Lookup (hasOwnProperty) Clarification

Profile Lookup (hasOwnProperty) Clarification


Tell us what’s happening:

I am confused as to why my original code does not work for this challenge. I used:

              if (contacts[i][prop] === prop) {

The code is only accepted if the following is used:

              if (contacts[i].hasOwnProperty(prop) {

Can someone clarify why I cannot check for the existence of the prop argument using the first method?


Your code so far

var contacts = [
        "firstName": "Akira",
        "lastName": "Laine",
        "number": "0543236543",
        "likes": ["Pizza", "Coding", "Brownie Points"]
        "firstName": "Harry",
        "lastName": "Potter",
        "number": "0994372684",
        "likes": ["Hogwarts", "Magic", "Hagrid"]
        "firstName": "Sherlock",
        "lastName": "Holmes",
        "number": "0487345643",
        "likes": ["Intriguing Cases", "Violin"]
        "firstName": "Kristian",
        "lastName": "Vos",
        "number": "unknown",
        "likes": ["Javascript", "Gaming", "Foxes"]

function lookUpProfile(firstName, prop){
// Only change code below this line
  for (var i = 0; i < contacts.length; i++) {
    if (contacts[i].firstName === firstName) {
      **if (contacts[i][prop] === prop) {**
        return contacts[i][prop];
      } else {
        return "No such property";
  return "No such contact";
// Only change code above this line

// Change these values to test your function
lookUpProfile("Akira", "firstName");

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.90 Safari/537.36.

Link to the challenge:


If you put the following console.log() statement:

console.log('contacts[i][prop] = ' + contacts[i][prop] + ' |  prop = ' + prop);

on the line before the following if statement:

      if (contacts[i][prop] === prop) {

then you will see:

contacts[i][prop] = Akira |  prop = firstName

Since “Akira” is not equal to “firstName”, the else block of code executes and returns “No such property”.

In this function call lookUpProfile(“Akira”, “firstName”);, prop is a variable with the value of “firstName”.

contact[i][prop] is the actual value of the current contact’s “firstName” property which in this case is “Akira”.


Ahh, that makes sense. Thanks for the breakdown!