Javascript Deep Comparison

Question

Questions about deep comparison of objects have been asked, and I have the solution. But there is a line in the solution that I don\'t completely understand.

This is the

Answer 1

The in operator returns true if the object on the right of the expression contains a key with the value of the string on the left of the expression.

Eg: prop in a is true if a contains a key with the same name as the string value of prop. Eg:

var prop = "age";

var obj1 = {
    name: "Dave",
    age: 21,
    record: { ... }
};
var obj2 = {
    name: "John",
    record: { ... }
};

console.log(prop in obj1); // true
console.log(prop in obj2); // false

If prop was set to "record" then deepEqual(a[prop], b[prop]) recursively compares the values in a.record and b.record.