One line utility function to determine if a certain key or a point separated key list exists on any given object for Javascript. Also accounts for empty strings and all other falsey values.

keyexists.js

// Regular Javascript version (in the end we have to evaluate the return into the proper boolean, an empty string is
// falsey in Javascript, but in this case we want it to behave as truthy. The OR operator with: '|| 1' is there to 'cast'
// false property values into a truthy value.
var keyExistsOn = (o, k) => k.split(".").reduce((a, c) => a.hasOwnProperty(c) ? a[c] || 1 : false, Object.assign({}, o)) === false ? false : true;

// Curried Javascript version, with the same boolean evaluation at the end.
var keyExistsOn = (k) => (o) => k.split(".").reduce((a, c) => a.hasOwnProperty(c) ? a[c] || 1 : false, Object.assign({}, o)) === false ? false : true;

// OUTPUT

var obj = {
    test: "",
    locals: {
        test: "",
        test2: false,
        test3: NaN,
        test4: 0,
        test5: undefined,
        auth: {
            user: "hw"
        }
    }
}

keyExistsOn(obj, "")
> false
keyExistsOn(obj, "locals.test")
> true
keyExistsOn(obj, "locals.test2")
> true
keyExistsOn(obj, "locals.test3")
> true
keyExistsOn(obj, "locals.test4")
> true
keyExistsOn(obj, "locals.test5")
> true
keyExistsOn(obj, "sdsdf")
> false
keyExistsOn(obj, "sdsdf.rtsd")
> false
keyExistsOn(obj, "sdsdf.234d")
> false
keyExistsOn(obj, "2134.sdsdf.234d")
> false
keyExistsOn(obj, "locals")
> true
keyExistsOn(obj, "locals.")
> false
keyExistsOn(obj, "locals.auth")
> true
keyExistsOn(obj, "locals.autht")
> false
keyExistsOn(obj, "locals.auth.")
> false
keyExistsOn(obj, "locals.auth.user")
> true
keyExistsOn(obj, "locals.auth.userr")
> false
keyExistsOn(obj, "locals.auth.user.")
> false
keyExistsOn(obj, "locals.auth.user")
> true

See this NPM package: https://www.npmjs.com/package/has-deep-value