Checking if object key exists and is true in one statement

Question

I have a javascript object that may or may not contain a certain key which may or may not be true;

{
    myKey: true,
}

I want to test whether the key exists, and if it does exist, whether it is true. I could do it like this;

if (myObject.myKey == true) {
}

With the use of the loose equality operator == , the answer will be false if myKey is undefined or false and only true if it is true. However, eslint complains 'Expected '===' and instead saw '=='. eslint(eqeqeq)' 'Expected '===' and instead saw '=='. eslint(eqeqeq)' . Is this a valid warning, or should I just ignore it?

Answer 1

The == operator has many surprises, which is why eslint is discouraging it. In this case, what eslint suggests does exactly what you're asking for:

if (myObject.myKey === true) {
}

Differences with the == operator only occur here if the value exists and is not a boolean; eg the value 1 . Due to the type conversions, 1 == true is true, but 1 === true is false.

If you also want a true value for such cases, just write

if (myObject.myKey) {
}