Everything Be True

From: https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/everything-be-true

Intermediate Algorithm Scripting: Everything Be True


Check if the predicate (second argument) is truthy on all elements of a collection (first argument).

In other words, you are given an array collection of objects. The predicate pre will be an object property and you need to return true if its value is truthy. Otherwise, return false.

In JavaScript, truthy values are values that translate to true when evaluated in a Boolean context.

Remember, you can access object properties through either dot notation or [] notation.


truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return true.

truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return false.

truthCheck([{"user": "Tinky-Winky", "sex": "male", "age": 0}, {"user": "Dipsy", "sex": "male", "age": 3}, {"user": "Laa-Laa", "sex": "female", "age": 5}, {"user": "Po", "sex": "female", "age": 4}], "age") should return false.

truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastForward", "onBoat": null}], "onBoat") should return false

truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastForward", "onBoat": true}], "onBoat") should return true

truthCheck([{"single": "yes"}], "single") should return true

truthCheck([{"single": ""}, {"single": "double"}], "single") should return false

truthCheck([{"single": "double"}, {"single": undefined}], "single") should return false

truthCheck([{"single": "double"}, {"single": NaN}], "single") should return false

const truthCheck = (collection, pre) => collection.every(el => el[pre]);

[
    truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex"),
    truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") ,
    truthCheck([{"user": "Tinky-Winky", "sex": "male", "age": 0}, {"user": "Dipsy", "sex": "male", "age": 3}, {"user": "Laa-Laa", "sex": "female", "age": 5}, {"user": "Po", "sex": "female", "age": 4}], "age") ,
    truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastForward", "onBoat": null}], "onBoat") ,
    truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastForward", "onBoat": true}], "onBoat") ,
    truthCheck([{"single": "yes"}], "single"),
    truthCheck([{"single": ""}, {"single": "double"}], "single") ,
    truthCheck([{"single": "double"}, {"single": undefined}], "single") ,
    truthCheck([{"single": "double"}, {"single": NaN}], "single") ,
].forEach(result => console.log(result));

Output:

true
false
false
false
true
true
false
false
false