ES6 Map map-filter proposal.md

Specification:

Map.prototype.map = function(cb, context) { return new Map(Array.from(this).map(cb, context)); }
Map.prototype.filter = function(cb, context) { return new Map(Array.from(this).filter(cb, context)); }

Usage example:

new Map([['keya', 'valuea'], ['keyb', 'valueb']])
  .map(([key, value]) => [key + 1, value + 1])
  .filter(([key, value]) => key === 'keya1')
// Map {"keya1" => "valuea1"}

Array.from takes a second mapper argument.

@ljharb but it can't be bound to a context... right?

Map.prototype.map = function(cb, context) { return new Map(Array.from(this, cb, context)); }
Map.prototype.filter = function(cb, context) { return new Map(Array.from(this, context).filter(cb)); }

new Map([...m].map(cb));
new Map([...m].filter(cb));

Map.prototype.filter = function(cb, context) { return new Map(Array.from(this, identity, context).filter(cb)); }