Array.every返回false而不是true

Question

I'm working on something and I wrote this code that seems to return 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 }]);    // return false

The two map functions return the correct arrays ([1,2,3] for the first and [2,3] for the second), But every function does not for some reason.

Can anyone help me find the bug in the code?

Answer 1

Don't use in to check whether an element in an array.

Instead , use .indexOf method.

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

Answer 2

in can be used like this with coffeescript, but in JS, it's just a iterator operator. Try with:

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

There are some missing/wrong characters in your code, here is a complete working code:

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 ~validIds.indexOf(id); });
    };
}

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

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

Answer 3

If you want use in you need a bit change you validIds

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

 function checkValidUsers(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 check = checkValidUsers([ { id: 1 }, { id: 2 }, { id: 3 }]); document.getElementById('res').innerHTML = check([{ id: 2 }, { id: 3 }]); 

 <div id="res"></div>