typed-morph

High order functions (map, reduce, filter) to work with Javascript typed arrays. They don't make use of intermediate arrays for chaining, and instead takes advantage of the iterator protocol.

Installing

npm i typed-morph

Usage

map

var wrap = require('typed-morph');
var elements = new Uint16Array([1,2,3]);
var mapped = wrap(elements).map(function(e) { return e * 2 }).col();
    
// mapped now is a Uint16Array with [2,4,6] content

Alternatively, you can avoid invoking col and use the iterator:

var wrap = require('typed-morph');
var elements = new Uint16Array([1,2,3]);
// returns an object that matches the JS iterator protocol https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/The_Iterator_protocol
var iterator = wrap(elements).map(function(e) { return e * 2 });
    
console.log(iterator.next()); // { done: false, value: 2 }

filter

var wrap = require('typed-morph');
var elements = new Uint16Array([1,2,3,4]);
var filtered = wrap(elements).filter(function(e) { return e % 2 === 0 }).col();
    
// mapped now is a Uint16Array with [2,4] content

Alternatively, you can avoid invoking col and use the iterator:

var wrap = require('typed-morph');
var elements = new Uint16Array([1,2,3,4]);
// returns an object that matches the JS iterator protocol https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/The_Iterator_protocol
var filtered = wrap(elements).filter(function(e) { return e % 2 === 0 });
    
console.log(iterator.next()); // { done: false, value: 2 }

reduce

var elements = new Uint16Array([1,2,3,4]);

var sum = wrap(elements).reduce(function(value, current){ return value + current; }, 0);

console.log(sum); // 10

Chaining

Sometimes you need to perform multiple sequential operations on the same array. The typed-morpth implementation does not create any intermediate arrays until either col or reduce are invoked.

For example:

var elements = new Uint16Array([1,4,7,10]);
var iter = wrap(elements)
  .map(function(e) { return e + 1; })
  .filter(function(e){ return e % 2 === 0; });

// at this point no processing has taken place
iter.reduce(function(value, current) { return value + current; }, 0);

expect(sum).to.equal(10);

Acknowledgements

• Using this great seed project from @mgonto.