Why the if statement is not accepting bracket-notation instead of dot-notation? - javascript-objects

Question

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){
for (var i = 0; i < contacts.length; i++){
if (firstName === contacts[i].firstName) {
if (contacts[i][prop]) {
return contacts[i][prop];
} else {
return "No such property";
}
}
}
return "No such contact";
}
lookUpProfile("Akira", "likes");
This code runs perfectly. but if i use if (firstName === contacts[i] [firstName]) instead of if (firstName === contacts[i].firstName), it doesn't work. Why? Since either dot or bracket notation both can be used for accessing the objects property.

Answer 1

The brackets are for variables. If you want to use them with String literals, you could, but you have to quote them: contacts[i]['firstName']. But unless the property name contains restricted characters (such as another dot or a space), that is just silly.
Note that you already used it with i (which is a variable) to get the i-th element (and not a property called i).