Sorting multiple arrays at once

Question

I have 3 arrays :

• array 1 is "Name" John, Jim, Jack, Jill

• array 2 is "Age" 25, 30, 31, 22

• array 3 is "Gender" Male, Male, Male, Female

I have these all listed in a table with a sortable header. Now the sort works fine, it sorts by the "Name" column for example. How can i also make it sort the "Age" and "Gender" arrays to keep them correct. I need to sort all 3 simultaneously.

_nameArray.sort(function(a, b){
    return ((a < b) ? -1 : ((a > b) ? 1 : 0));
})

Hope it is explained well enough.

No the structure can not be changed, the way things are it has to be 3 arrays, not one and just sort by the field in the array.

Answer 1

Even though constructing Objects from the multiple arrays may be ideal. You can also do it without the object creation overhead using indirection.

/* An array of indexes */
var idx = [];
for (var i = 0; i < Name.length; i++) {
    idx.push(i);
}

/* A shorthand function */
var comparator = function(arr) {
    return function(a, b) {
        return ((arr[a] < arr[b]) ? -1 : ((arr[a] > arr[b]) ? 1 : 0));
    };
};

/* Sort by Age */
idx = idx.sort(comparator(Age));

/* Get the sorted order */
for (var i = 0; i < Name.length; i++) {
    console.log(Name[idx[i]], Age[idx[i]], Gender[idx[i]]);
}​

The idx array contains indexes to the elements of the other arrays, idx[i]. By using indirection you can access the element in Name, Age and Gender; that is, Name[idx[i]].

If performance is a problem then constructing the objects may be faster using in-place sorting, if you just do it once. Otherwise, I would use the indirection without never touching the real arrays.

There you go.

Note: The comparator function is just an example, you need to actually create your own comparator functions based on your criteria.

Answer 2

Having tried making objects (as suggested in some of the comments) I'm not sure the added complexity is worth it, but will post it here anyway in case it's useful. In this particular case a Person object serves little purpose and what is potentially more useful is an aggregate object (PersonSet) that will store the joint data, sort it, and deal with the lists of each type of characteristic as input and output. (jsfiddle)

var names = ['John', 'Jim', 'Jack', 'Jill'],
    ages = [25, 30, 31, 22],
    genders = ['male', 'male', 'male', 'female'];
function Person(name, age, gender) {
    this.name = name;
    this.age = age;
    this.gender = gender;
}
function PersonSet(names, ages, genders) {
    this.content = [];
    for (var i = 0; i < names.length; i++) {
        this.content.push(new Person(names[i], ages[i], genders[i]));
        // (alternatively...)
        // this.content.push({name: names[i], age: ages[i], gender: 
        //     genders[i]});
    }
    this.sort = function(aspect) {
        this.content.sort(function(a, b) {
            return ((a[aspect] < b[aspect]) ? -1 : 
                ((a[aspect] > b[aspect]) ? 1 : 0));
        });
    };                    
    this.get = function(aspect) {
        var r = [];
        for (var i = 0; i < this.content.length; i++) {
            r.push(this.content[i][aspect]);
        }
        return r;
    }
}
var personSet = new PersonSet(names, ages, genders);
personSet.sort('age');
console.log(personSet.get('name'), personSet.get('age'), 
            personSet.get('gender'));​​​​​​​​​​