The result of Array.every is opposite to what was expected, returning false

Question

The result of Array.every is opposite to what was expected, returning false

Currently, I'm facing an issue with my code where it is returning false instead of true:

function checkValidUsers(validUsers) 
{
    var validIds = validUsers.map(function (user) { return user.id; });

    return function (users) 
    {
        var ids = users.map(function (user) { return user.id; });
        return ids.every(function (id) { return id in validIds; } );
    }
}

var check = checkValidUsers([{ id: 1 }, { id: 2 }, { id: 3 }]);

check([{ id: 2 }, { id: 3 }]);    // returns false

Upon examining the map functions, they are correctly generating arrays ([1,2,3] for the first and [2,3] for the second). However, it seems that the issue lies within the every function.

I am seeking assistance to identify and resolve the bug in this code. Can anyone provide insights?

javascript arrays function dynamic-arrays

Answer 1

Answer №1

Avoid using the in keyword to verify if an element is in an array.

Instead, opt for the .indexOf method.

return ids.every(function (id) { return validIds.indexOf(id) !== -1; });

Answer 2

Avoid using the in keyword to verify if an element is in an array.

Instead, opt for the .indexOf method.

return ids.every(function (id) { return validIds.indexOf(id) !== -1; });

Answer 3

Answer №2

in can be utilized in coffeescript in this way, however, in JS, it functions as an iterator operator. Give it a shot with:

return ids.every(function (id) { return ~validIds.indexOf(id); });

Your code contains some incorrect/missing characters; here's a complete working version:

function validateUserList(validUsers) {
    var validIds = validUsers.map(function (user) { return user.id; });

    return function (users) {
        var ids = users.map(function (user) { return user.id; });
        return ids.every(function (id) { return ~validIds.indexOf(id); });
    };
}

var validationFunction = validateUserList([
    { id: 1 }, { id: 2 }, { id: 3 }
]);

validationFunction([{ id: 2 }, { id: 3 }]);

Answer 4

in can be utilized in coffeescript in this way, however, in JS, it functions as an iterator operator. Give it a shot with:

return ids.every(function (id) { return ~validIds.indexOf(id); });

Your code contains some incorrect/missing characters; here's a complete working version:

function validateUserList(validUsers) {
    var validIds = validUsers.map(function (user) { return user.id; });

    return function (users) {
        var ids = users.map(function (user) { return user.id; });
        return ids.every(function (id) { return ~validIds.indexOf(id); });
    };
}

var validationFunction = validateUserList([
    { id: 1 }, { id: 2 }, { id: 3 }
]);

validationFunction([{ id: 2 }, { id: 3 }]);

Answer 5

Answer №3

If you wish to utilize the in keyword, some adjustments are required in your validIds

var validIds = validUsers.reduce(function (acc,user) {  
    acc[user.id]=true; 
    return acc; 
},{});

function verifyValidUsers(validUsers) {
    var validIds = validUsers.reduce(function (acc,user) {  acc[user.id]=true; return acc; },{}); 

    return function (users) {
         var ids = users.map(function (user) { return user.id; });
         return ids.every(function (id) { return id in validIds; });
    }
}

var verify = checkValidUsers([
     { id: 1 }, { id: 2 }, { id: 3 }]);

document.getElementById('result').innerHTML = check([{ id: 2 }, { id: 3 }]);

<div id="result"></div>

Answer 6

If you wish to utilize the in keyword, some adjustments are required in your validIds

var validIds = validUsers.reduce(function (acc,user) {  
    acc[user.id]=true; 
    return acc; 
},{});

function verifyValidUsers(validUsers) {
    var validIds = validUsers.reduce(function (acc,user) {  acc[user.id]=true; return acc; },{}); 

    return function (users) {
         var ids = users.map(function (user) { return user.id; });
         return ids.every(function (id) { return id in validIds; });
    }
}

var verify = checkValidUsers([
     { id: 1 }, { id: 2 }, { id: 3 }]);

document.getElementById('result').innerHTML = check([{ id: 2 }, { id: 3 }]);

<div id="result"></div>

The result of Array.every is opposite to what was expected, returning false

Answer №1

Answer №2

Answer №3

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