Copying element of existing array to a a new array without using splice?

Question

I'm currently doing some coursework for university. I am trying to copy an individual value of an old array to a new array, then setting the old arrays value to 0. Obviously if i just assign the value to the new array, then alter the old arrays value, it will overwrite the new array too.

I am not allowed to use the function splice().

here is my code:

function rankedScores(web, pattern) {
    var v = urlScores(web, pattern);
    var sorted = [];
    var maxIndex = 0;
    while (sorted.length < v.length) {
        for (var i = 0; i < v.length; i += 1) {

            if (v[i].score > v[maxIndex].score) {
                maxIndex = i
            }
        }
        sorted[sorted.length] = v[maxIndex];
        v[maxIndex].score = 0;

        maxIndex = 0;
    }
    alert(sorted[0].url + '   ' + sorted[0].score)
    alert(sorted[1].url + '   ' + sorted[1].score)
    alert(sorted[2].url + '   ' + sorted[2].score)
}

If i do this it returns the correct URL value, but all the score values are 0.

Any ideas on how i can stop the arrays from pointing to the same memory location?

Ive tried using a for loop as ive seen this does a shallow copy, but it didnt work

Cheers.

One option would be to just negate the score and then set it back in a secondary loop. Another to just set the whole array entry to null and to check for that before doing the comparison... — Stefan Haustein
– Stefan Haustein, Commented Nov 10, 2013 at 15:17

Emissary · Accepted Answer · 2013-11-10 15:13:31Z

1

Replace:

sorted[sorted.length] = v[maxIndex];
v[maxIndex].score = 0;

with:

// ...

var clone = {};
for(var i in v[maxIndex])
    clone[i] = v[maxIndex][i];
sorted[sorted.length] = clone;

v[maxIndex].score = 0;

// ...

Of course, you haven't stated how deep your objects are - I assume they are simple key:value maps but this should be enough to steer you in the right direction.

answered Nov 10, 2013 at 15:13

Emissary

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1 Comment

mwild Over a year ago

Thank you!! worked a charm. I had tried using a loop to replace the value but i didnt consider using a seperate variable to store the record. Thanks very much!!

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