Sort two arrays the same way

Question

For example, if I have these arrays:

var name = [\"Bob\",\"Tom\",\"Larry\"];
var age =  [\"10\", \"20\", \"30\"];

And I use name.sort

Answer 1

I was looking for something more generic and functional than the current answers.

Here's what I came up with: an es6 implementation (with no mutations!) that lets you sort as many arrays as you want given a "source" array

/**
 * Given multiple arrays of the same length, sort one (the "source" array), and
 * sort all other arrays to reorder the same way the source array does.
 * 
 * Usage:
 * 
 * sortMultipleArrays( objectWithArrays, sortFunctionToApplyToSource )
 * 
 * sortMultipleArrays(
 *   {
 *    source: [...],
 *    other1: [...],
 *    other2: [...]
 *   },
 *   (a, b) => { return a - b })
 * )
 * 
 * Returns:
 *   {
 *      source: [..sorted source array]
 *      other1: [...other1 sorted in same order as source],
 *      other2: [...other2 sorted in same order as source]
 *   }
 */
export function sortMultipleArrays( namedArrays, sortFn ) {
    const { source } = namedArrays;
    if( !source ) {
        throw new Error('You must pass in an object containing a key named "source" pointing to an array');
    }

    const arrayNames = Object.keys( namedArrays );

    // First build an array combining all arrays into one, eg
    // [{ source: 'source1', other: 'other1' }, { source: 'source2', other: 'other2' } ...]
    return source.map(( value, index ) =>
        arrayNames.reduce((memo, name) => ({
            ...memo,
            [ name ]: namedArrays[ name ][ index ]
        }), {})
    )
    // Then have user defined sort function sort the single array, but only
    // pass in the source value
    .sort(( a, b ) => sortFn( a.source, b.source ))
    // Then turn the source array back into an object with the values being the
    // sorted arrays, eg
    // { source: [ 'source1', 'source2' ], other: [ 'other1', 'other2' ] ... }
    .reduce(( memo, group ) =>
        arrayNames.reduce((ongoingMemo, arrayName) => ({
            ...ongoingMemo,
            [ arrayName ]: [
                ...( ongoingMemo[ arrayName ] || [] ),
                group[ arrayName ]
            ]
        }), memo), {});
}