I am trying to understand the difference between .Notation
and []
notation. In my problem below when I use if (object[key] === true)
I get the correct answer. When I use if (object.key === true)
it does not work. Could someone explain why it's different.
var myObj = {
one: false,
two: false,
three: false,
four: true,
five: false,
six: false
};
var myFunc = function (object) {
for (var key in object) {
if (object[key] === true) {
return "There is a true value in this object";
} else {
}
}
return "Sorry, there are no true values in this object";
};
When you use dot notation, key
means the actual property in the object, which will not be there. So, undefined
is returned which is not equal to true
.
When you use []
notation you are accessing the property in the object with the name in the variable key
. So, that will work.
For example,
var myObj = {
myVar : 1
};
for (var key in myObj) {
console.log(key);
console.log(myObj.key);
console.log(myObj[key]);
}
This will print,
myVar
undefined
1
Because, myObj
has no member named key
(myObj.key
tries to get the member with the name key
) and in the next case, myObj
has a member named myVar
(myObj[key]
tries to get the member with the value in key
).
Dot Notation
[] Notation
This offers flexibility. You can dynamically access the members with a variable.