how to access and sort 2d array in javascript

Question

I'm writing a script to initalize 2d array in javascript by reading txt file. Here are some portions of my code

var neighbor = {};
var temp = new Array();
neighbor[nodemap[ temparray[0]]] = temp; //nodemap[ temparray[0]] is an integer
neighbor[nodemap[temparray[0]]]. push(nodemap[temparray[1]]);
neighbor[nodemap[temparray[0]]]. push(nodemap[temparray[2]]);
.... // continue to add value

Then I want to access and sort the array, like this

for (var i = 0; i < n_count; i++);
{
  for (var k = 0; k < neighbor[i].length; k++);
    neighbor[k].sort(function(a,b){return a - b})
}

However, I got the error that neighbor[i] is unidentified. Could you please show me how to fix that?

i guess u should have used 'k' instead of i ? is 'i' in scope ? — dreamweiver
– dreamweiver, Commented Apr 5, 2013 at 14:32
Sorry, it's k... I made mistakes, i editted the post already — Josh Vo
– Josh Vo, Commented Apr 5, 2013 at 14:34

Ian · Accepted Answer · 2013-04-05 14:44:54Z

1

Your neighbor "array" is actually an object literal. So the way you should loop over neighbor is:

for (var key in neighbor) {
    var cur = neighbor[key];
    cur.sort(function (a,b) {
        return a - b;
    });
}

edited Apr 5, 2013 at 14:44

answered Apr 5, 2013 at 14:29

Ian

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7 Comments

Anthony Grist Over a year ago

If neighbor[i] is undefined then neighbor[i][k] won't be accessible either. I also think neighbor[i] is supposed to be an array that they want to sort.

Ian Over a year ago

@AnthonyGrist Yeah I'm starting to realize a few things. I've been editing to explain more. Thanks for pointing it out

Ian Over a year ago

@JoshVo I know, I've been editing my answer. I just finished. Does that help? Can you provide a jsFiddle with your actual filling of neighbor?

Josh Vo Over a year ago

thanks Ian. It works. However, I still need to write back right? (i.e neighbor[key] = cur;) Is there any method I could sort directly? I am working with a very large data...

Ian Over a year ago

@JoshVo No, you don't need to write back. When you have var cur = neighbor[key];, cur will be a reference to the specific array in neighbor. So it gets modified in place. Here's an example - jsfiddle.net/DwaAa . And I can't think of any other way to sort these

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