Unknown Javascript error

Question

I am trying to sort an array into descending order.

This is my current code:

for(var i = 0; i < scoresArray.length; i){
function swap(a, b) {
            var temp = scoresArray[a].score;
            scoresArray[a] = scoresArray[b].score;
            scoresArray[b] = temp;
}
    for(var x = 0; x < scoresArray.length; x++){
        if(scoresArray[x].score < scoresArray[++x].score){
            console.log(x);
            swap(x, ++x);
        }
    }
}
return scoresArray.content;

This is the input array:

  [
    { url: 'www.lboro.ac.uk', score: 6 },
    { url: 'www.xyz.ac.uk', score: 3 },
    { url: 'www', score: 8 } ]

This (should be) the output array:

  [{ url: 'www.xyz.ac.uk', score: 3 },
    { url: 'www.lboro.ac.uk', score: 6 },
    { url: 'www', score: 8 } ]

Answer 1

Like @Douglas said, using array.sort(compareFunction) makes this easier:

var scoresArray = [
    { url: 'www.lboro.ac.uk', score: 6 },
    { url: 'www.xyz.ac.uk', score: 3 },
    { url: 'www', score: 8 } ];
scoresArray.sort(function(a,b) {
    return a.score - b.score;
});

Note that, since scoresArray[i].score are numbers, you can use return a.score - b.score . In a more general case (eg if they were strings), you could use

scoresArray.sort(function(a,b) {
    if(a.score > b.score) return 1;
    if(a.score < b.score) return -1;
    return 0;
});

Answer 2

The swap function isn't working, it replaces the values in scoresArray with just the score numbers. It is also important to know that ++x changes the value of x . I think you mean x + 1 instead.

This roughly works:

var scoresArray = [
    { url: 'www.lboro.ac.uk', score: 6 },
    { url: 'www.xyz.ac.uk', score: 3 },
    { url: 'www', score: 8 } ];

function swap(a, b) {
    var temp = scoresArray[a];
    scoresArray[a] = scoresArray[b];
    scoresArray[b] = temp;
}

for(var i = 0; i < scoresArray.length; i++) {
    for(var x = 0; x < scoresArray.length - 1; x++) {
        if (scoresArray[x].score > scoresArray[x + 1].score) {
            swap(x, x + 1);
        }
    }
}

console.log(scoresArray);

But it would be better to use array.sort:

var scoresArray = [
    { url: 'www.lboro.ac.uk', score: 6 },
    { url: 'www.xyz.ac.uk', score: 3 },
    { url: 'www', score: 8 } ];

scoresArray.sort(function(a, b) {
    return b.score - a.score;
});

console.log(scoresArray);