In JS a Boolean has 4 states.
true
false
undefined (where the key is set to undefined)
undefined (where the key doesn’t exist on the object)

if (obj.value === true) {  
    console.log(1);
} else if (obj.value === false) {
    console.log(2);
} else if ("value" in obj) { // key "value" is in the obj, but it is set to undefined 
    console.log(3);
} else { // key "value" is not in object
    console.log(4);
}

You’re welcome.