Checking if a key exists in a JavaScript object?

Question

How do I check if a particular key exists in a JavaScript object or array?

If a key doesn\'t exist, and I try to access it, will it return false? Or throw an error?<

Answer 1

a fast and easy solution is to convert your object to json then you will be able to do this easy task

    const allowed = {
        '/login' : '',
        '/register': '',
        '/resetpsw': ''
    };
    console.log('/login' in allowed); //returns true

if you use an array the object key will be converted to integers ex 0,1,2,3 etc, therefore, it will always be false