How check an object's every key and value if null or undefined with ES6?-CodePudding

I'm trying to check an objects every entry's key and value in a if condition, but i cannot understand my result. What is the problem? Why is an undefined not false with "??" ?

const object = {undefined: "foo", B: "Bazz"}
console.log(Object.entries(object).every(([key, value]) => !!key && !!value))

//true

const object2 = {undefined: null, B: "Bazz"}
console.log(Object.entries(object2).every(([key, value]) => !!key && !!value)) 

//false

CodePudding user response：

You cannot actually set the key to undefined. When you do { undefined: "foo" }, you are actually setting the key to the string "undefined". It is essentially the same as { "undefined": "foo" }

!!"undefined" && !!"foo" => true && true => true because non-empty strings are truthy

!!"undefined" && !!null => true && false => false because null is falsy

CodePudding user response：

The propertie names of objects are strings or Symbol. To check the value, you could take an array of unwanted strings and check with includes.

const
    check = object => Object
        .entries(object)
        .every(([key, value]) => !['', 'null', 'undefined'].includes(key) && value);

console.log(check({ a: "foo", B: "Bazz" }));
console.log(check({ undefined: "foo", B: "Bazz" }));
console.log(check({ undefined: null, B: "Bazz" }));