ArrayToolbox

Collection of frequently useful array algorithms, mostly for use with Array.prototype.filter and Array.prototype.reduce.

Core

intersection

ArrayToolbox.Core.intersection([1, 2, 1, 3], [1, 1, 1]);
// Returns `[1, 1]`.

modalValues

ArrayToolbox.Core.modalValues([2, 1, 1, 3, 2]);
// Returns `[2, 1]`.

Filter

unique

[2, 1, 1, 3, 2].filter( ArrayToolbox.Filter.unique());
// Returns `[1, 3, 2]`.

Reduce (Accumulate)

defaultIfEmpty

[]
    .reduce( ArrayToolbox.Reduce.defaultIfEmpty(), [5])
    .reduce( ArrayToolbox.Reduce.firstOrDefaultTo(), null );
// Returns `5`, not `null`.

findAllIndexes

[2, 1, 1, 3, 2].reduce( ArrayToolbox.Reduce.findAllIndexes( 2 ), []);
// Returns `[0, 4]`.

firstOrDefaultTo

// Get minimum value of an array of objects.
let collator_comparator = function( left, right )
    {return( this.compare( left.value, right.value ));}
    .bind( new Intl.Collator([], {"numeric":true}));
let array =
[
    {"value":5},
    {"value":3},
    {"value":4}
];
array
    .sort( collator_comparator )
    .reduce( ArrayToolbox.Reduce.firstOrDefaultTo(), null );
// Returns `{"value":3}`.

lastOrDefaultTo

// Get maximum value of an array of objects.
let collator_comparator = function( left, right )
    {return( this.compare( left.value, right.value ));}
    .bind( new Intl.Collator([], {"numeric":true}));
let array =
[
    {"value":5},
    {"value":3},
    {"value":4}
];
array
    .sort( collator_comparator )
    .reduce( ArrayToolbox.Reduce.lastOrDefaultTo(), null );
// Returns `{"value":5}`.

singleOrDefaultTo

// Assert array is empty or contains only one element.
let array =
[
    {"value":5},
    {"value":3},
    {"value":4}
];
array
    .filter( function( each, n, every )
    {return( each.value > 3 );})
    .reduce( ArrayToolbox.Reduce.singleOrDefaultTo(), null );
// Throws `RangeError: 'array' should be of length 0 or 1.`.