AngularJS - Javascript: Is there anything I can do to improve this valid-state function?

Question

I have this function in an AngularJS service:

self.IsValid = function (entity) {
    if (entity == undefined || entity == "undefined")
        return false;

    if (entity == null)
        return false;

    if (entity == "00000000-0000-0000-0000-000000000000")
        return false;

    return true;
}

A working sample here.

Is there anything I can do to improve on this? Or maybe there's a better way altogether?

PS: Resharper says that the entity == null check is always false, but that doesn't feel right, I could have passed null.

Answer 1

You can use

self.IsValid = function(entity) {
    return (entity !== "undefined" && entity !== "00000000-0000-0000-0000-000000000000") && !!entity;
};

1. entity !== "undefined" && entity !== "00000000-0000-0000-0000-000000000000": Checks if the value of entity variable is not 'undefined' and '00000000-0000-0000-0000-000000000000'. If the expression evaluates to false the result will be returned.
2. !! will cast the value to Boolean. See What is the !! (not not) operator in JavaScript?

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