CODEWITHSUNDEEP
javascriptalgorithmsorting
Subpar Web Dev
Subpar Web Dev

Reputation: 3260

Why isn't this sorting correctly?

So I'm attempt to take an array like

 ["2015/10","2015/1","2015/6","2015/12","2015/3","2015/7","2015/2","2016/1","2015/8","2015/5","2015/11","2015/9","2015/4"]

, where the XXXX/YY is year/month format, and sort it from least to greatest.

Attempt, using https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort as a reference: 

month_keys.sort(function(x,y){
    var partsX = x.split('/'), partsY = y.split('/');
    return partsX[0] < partsY[0] ? -1 : ( partsX[1] < partsY[1] ? -1 : 1 );
})...

and that gives me

 ["2015/1","2015/11","2016/1","2015/10","2015/12","2015/2","2015/3","2015/5","2015/5","2015/6","2015/7","2015/8","2015/9"]

in the example array I gave at the beginning. What am I doing wrong?

Upvotes: 1

Views: 59

Answers (2)

chapelo
chapelo

Reputation: 2562

You have strings representing numbers. Just put a '+' before the variable to convert it to number:

return +partsX[0] < +partsY[0] ? -1 : ( +partsX[1] < +partsY[1] ? -1 : 1 );

I works...

Upvotes: -1

ThiefMaster
ThiefMaster

Reputation: 318468

You are comparing strings, not numbers. When comparing strings, they are compared char by char so anything starting with an 1 comes before something starting e.g. with a 2. Even if it's 10 vs 2.

Convert them to numbers and you should get the order you want:

var partsX = +x.split('/'),
    partsY = +y.split('/');

You also need to fix the actual comparison:

if (partsX[0] < partsY[0]) return -1;
else if (partsX[0] > partsY[0]) return 1;
else if (partsX[1] < partsY[1]) return -1;
else if (partsX[1] > partsY[1]) return 1;
else return 0;

Upvotes: 5

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