Basic JavaScript - Using Objects for Lookups

Tell us what’s happening:

My code works but when I do result= lookup.val; dot notation, it doesn’t work. I wonder why? As I know u can use dot or bracket notation to get value

Your code so far

// Setup
function phoneticLookup(val) {
  let result = "";

  // Only change code below this line
  const lookup = {
    "alpha": "Adams",
    "bravo": "Boston",
    "charlie": "Chicago",
    "delta": "Denver",
    "echo": "Easy",
    "foxtrot": "Frank"
  result = lookup[val];
  // Only change code above this line
  return result;


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Challenge Information:

Basic JavaScript - Using Objects for Lookups


This one was very astonishing for me to learn. You see dot notation . only deals with static keys. That is keys aren’t programmatically assigned. Right now the lookup is trying to find a value called “val” in the object, that simply doesn’t exist.

Bracket notation however doesn’t have this problem. It can have literally any key during runtime.

Source: Dot Notation vs Bracket Notation for Object Properties – What's the Difference?

Happy learning. :slight_smile:


lookup.val is equivalent to lookup["val"]

The lookup object doesn’t have a key named “val”.


Oh I thought . can be also used to assign a parameter. so it is only [] when u r trying to assign a parameter