array-filter-map

Filter and map in one trip through the target array.

Why?

• Faster for large arrays than chaining filter and map (negligable for small ones...). Only goes through the target array once. Uses Array.prototype.reduce().
• Intuitive pattern is almost identical to Array.prototype.filter and Array.prototype.map, so use the same pattern when you have to do both instead of writing another one in Array.prototype.reduce.
• Reusable, avoid writing reduce to do both tasks every time you need it.

Why Not?

• It's not THAT much more efficient for small arrays.
• It's not that hard to write it yourself.

Install

npm install array-filter-map

Signature:

function arrayFilterMap<T,R>(
    targetArray: T[],
    filterCallback: (element: T, index: number, origArray: T[]) => boolean,
    mapCallback: (element: T, index: number, origArray: T[]) => R,
    thisArg?: any
): R[];

Example Usage:

const filtermap = require('array-filter-map');

const testArray = [{id: 1, value: 'test 1'}, {id: 2, value: 'test 2'}, {id: 3, value: 'test 3'}];
const newArray = filtermap(
    testArray,
    element => element.id === 2,
    element => element.value
);
// newArray = ['test 2']

Of Note:

The index parameter in the mapCallback will reference the index of the element in the original array, but possibly not the resultant array depending on the results of the filterCallback.

Test Results (jest):

  arrayFilterMap test suite
    ✓ should return a new array (3ms)
    ✓ should map each item of the array to its "id" propery (1ms)
    ✓ should filter out all values (1ms)
    ✓ should warn about index usage in map
    ✓ should use thisArg as "this" when passed as 4th argument (1ms)
    ✓ should use the index and origArray parameters as specified for each callback
    ✓ should throw an error for filterCallback not a function (2ms)
    ✓ should throw an error for mapCallback not a function (1ms)
    ✓ this  --->                  (arrayFilterMap()): (63ms)
    ✓ ...should be faster than this (filter().map()): (124ms)
    ✓ but...       about the same as this (reduce()): (72ms)