Using Brackets[] and dots(.)to access properties in an object

[Briankipkoech]

/* so guys pleas help me on this!!
am having a hard time trying to understand why is it when i use …
return obj.prop the console output is ….undefind, but if i use obj[prop]
the console output is Brian Oneal,

*/

const myFamily={
“me”:“Brian Oneal”
};

function testObject(obj,prop){
if(obj.hasOwnProperty(prop)){
return obj.prop;
}
else { return “Not found”;

}
}
console.log(testObject(myFamily,“me”))

output=undefind

[kevinSmith]

@Briankipkoech

return obj.prop;

This evaluate the property named “prop” on object obj.

If you are hard coding the property name, you can use dot notation:

const obj = {
 foo: 'bar',
}
console.log(obj.foo)
// bar

If you don’t know what actual property name is, like it is in a variable, you have to use bracket notation:

const obj = {
  foo: 'bar',
}

const propName = 'foo'

console.log(obj[propName])
// foo

console.log(obj.propName)
// undefined, because there is no property named "propName"

The other time you have to use bracket notation is if the property name is not a valid JS identifier, e.g., it starts with a number, has a hyphen in it, has a space in it, etc.

const obj = {
  'my-name': 'Kevin',
}

console.log(obj['my-name'])
// Kevin

console.log(obj.my-name)
// gives you an error

Notice that when I declared the object, I also had to wrap the property name in quotes, for the same reason.

[Briankipkoech]

thanks . …fam
wished free code camp had explained it the way you did, it would make thinks much smoother in here