tracking indexes with a shuffle algorithm in javascript

Question

I have an simple array of strings that looks like the one below and a corresponding new array. What I need to accomplish is to is to shuffle the the simple array with a simple shuffle algorithm (like the one below), but I need the corresponding new array to to be shuffled with the same exact shuffle, that is the result of each index would be identical. That may be confusing so look at the example output below and it should become clear. Is this type of algorithm even possible with Fisher-Yates shuffle?

Fiddle: here

Before:

var simple_arr = ["701", "702", "703", "704", "705", "706", "707", "708"];
var new_arr = ["A1","A2","A3","A4","A5","A6","A7","A8"];

After:

var after_simple_arr = ["701", "708", "702", "705", "703", "706", "704", "707"];
var after_new_arr = ["A1","A8","A2","A5","A3","A6","A4","A7"];

Fisher-Yates shuffle algorithm:

function shuffle(array) {
  var currentIndex = array.length, temporaryValue, randomIndex;

  // While there remain elements to shuffle...
  while (0 !== currentIndex) {

    // Pick a remaining element...
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;

    // And swap it with the current element.
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }
  return array;
}

zw324 · Accepted Answer · 2016-06-23 02:34:11Z

1

You could shuffle an index array then use it as the index for the two arrays you care about:

var ids = [];
for (var i = 0; i < simple_arr.length; i++) {
    ids.push(i);
}
ids = shuffle(ids);
var dat1 = [];
var dat2 = [];
for (var i = 0; i < ids.length; i++) {
    dat1.push(simple_arr[ids[i]]);
  dat2.push(new_arr[ids[i]]);
}
console.log("shuffled simple_arr: ", dat1);
console.log("shuffled new_arr: ", dat2);

answered Jun 23, 2016 at 2:34

zw324

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Comments

le_m · Accepted Answer · 2016-06-23 02:38:26Z

0

Just shuffle an index array indices = [0, 1, 2, ...] and then use it to access your to-be-shuffled-by-the-same-permutation arrays via array[indices[i]].

answered Jun 23, 2016 at 2:38

le_m

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