Adonis K.

I'm certain a lot of you have had this issue in the past, I did too. So, let me demostrate to you have to quickly solve this issue without almost no change in your current code.

var person = {};
if(person.name.first === "John"){
    console.log(person.name.first);
}

The code above will output the following error string Uncaught TypeError: Cannot read property 'first' of undefined in the JavaScript console. To fix this issue, you need to first check whether the object path you are trying to check exists.

var person = {};
if(person.name && person.name.first === "John"){
    console.log(person.name.first);
} else {
    console.log('no name given to this person');
}

This way you won't get any errors or broken code in production.