ptrn ptrn - 2 months ago 12
Javascript Question

sort outer array based on values in inner array, javascript

I have an array with arrays in it, where I want to sort the outer arrays based on values in a specific column in the inner.

I bet that sounded more than a bit confusing, so I'll skip straight to an example.

Initial data:

var data = [
[
"row_1-col1",
"2-row_1-col2",
"c-row_1-coln"
],
[
"row_2-col1",
"1-row_2-col2",
"b-row_2-coln"
],
[
"row_m-col1",
"3-row_m-col2",
"a-row_m-coln"
]
];


Sort data, based on column with index 1

data.sortFuncOfSomeKind(1);


where the object then would look like this;

var data = [
[
"row_2-col1",
"1-row_2-col2",
"b-row_2-coln"
],
[
"row_1-col1",
"2-row_1-col2",
"c-row_1-coln"
],
[
"row_m-col1",
"3-row_m-col2",
"a-row_m-coln"
]
];


Sort data, based on column with index 2

data.sortFuncOfSomeKind(2);


where the object then would look like this;

var data = [
[
"row_m-col1",
"3-row_m-col2",
"a-row_m-coln"
],
[
"row_2-col1",
"1-row_2-col2",
"b-row_2-coln"
],
[
"row_1-col1",
"2-row_1-col2",
"c-row_1-coln"
]
];


The big Q

Is there an existing solution to this that you know of, or would I have to write one myself? If so, which would be the easiest sort algorithm to use? QuickSort?

_L

Answer

Array#sort (see section 15.4.4.11 of the spec, or MDC) accepts an optional function parameter which will be used to compare two entries for sorting purposes. The function should return -1 if the first argument is "less than" the second, 0 if they're equal, or 1 if the first is "greater than" the second. So:

outerArray.sort(function(a, b) {
    var valueA, valueB;

    valueA = a[1]; // Where 1 is your index, from your example
    valueB = b[1];
    if (valueA < valueB) {
        return -1;
    }
    else if (valueA > valueB) {
        return 1;
    }
    return 0;
});

(You can obviously compress that code a bit; I've kept it verbose for clarity.)