Prevent initial array from sorting

Question

I have an array where the order of the objects is important for when I finally output the array in a document. However, I'm also sorting the array in a function to find the highest value. The problem is that I after I run the function to find the highest value, I can't get the original sort order of the array back.

// html document
var data = [75,300,150,500,200];

createGraph(data);

// js document

function createGraph(data) {

    var maxRange = getDataRange(data);

    // simpleEncode() = google encoding function for graph
    var dataSet = simpleEncode(data,maxRange);

}

function getDataRange(dataArray) {
    var num = dataArray.sort(sortNumber);
    return num[0];
}

I've also tried setting data to dataA and dataB and using dataB in the getDataRange function and dataA in the simpleEncode function. Either way, data always end up being sorted from highest to lowest.

Any of the answers posted so far will solve your problem.

Matt Ball
– Matt Ball

2010-04-26 15:26:42 +00:00
Commented Apr 26, 2010 at 15:26 — Matt Ball
– Matt Ball, Commented Apr 26, 2010 at 15:26

SLaks · Accepted Answer · 2010-04-26 15:18:08Z

9

As you've discovered, sorting an array modifies the array in-place.
To prevent that, you need to sort() a separate copy of the array, so that the original array is not affected.

You can copy an array by calling slice():

var num = dataArray.slice().sort(sortNumber);

answered Apr 26, 2010 at 15:18

SLaks

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Comments

Christian C. Salvadó · Accepted Answer · 2010-04-26 15:23:22Z

5

You can find the highest value of your array simply by applying the Math.max method to it, you don't need to sort it:

function getDataRange(dataArray) {
  return Math.max.apply(Math, dataArray);
}

answered Apr 26, 2010 at 15:23

Christian C. Salvadó

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2 Comments

Christian C. Salvadó Over a year ago

You're welcome @George, try it out, IMO apply can be faster than sorting a copy of your original array.

Choy Over a year ago

I just tried this method and it works great. My array contains only 6 objects, so I don't see any speed difference, but will definitely keep it in mind in the future.

Ray · Accepted Answer · 2010-04-26 15:22:20Z

2

Rather than sorting the array to get the highest value, just use a for or foreach loop to walk through it and find the highest value. It will be faster than sorting, and will leave your array unchanged.

answered Apr 26, 2010 at 15:22

Ray

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Comments

Jerry Coffin · Accepted Answer · 2010-04-26 15:22:27Z

0

Two possibilities: either sort a copy of the array (fine as long as it's not too big) or else scan through the array to find the largest item without sorting it at all.

answered Apr 26, 2010 at 15:22

Jerry Coffin

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