What if Underscore was written in ES6
Would ES6 have changed Underscore externally?
(I think so.)
Problem #1
var activeUsers = _.filter(users, function(user) { return user.isActive });
var ages = _.map(activeUsers, function(user) { return user.age });
var maxAge = _.reduce(ages, max, 0);Problem #1: Wasteful intermediate arrays
var activeUsers = _.filter(users, function(user) { return user.isActive });
var ages = _.map(activeUsers, function(user) { return user.age });
var maxAge = _.reduce(ages, max, 0);Solution to problem #1: Generators
function* map(items, transform) {
for (item of items)
yield transform(item);
}
Notice how similiar this is to the previous code.
Solution to problem #2: Iterators
var iterable = {};
iterable[iterator] = function() { /* ... */ };
Solution to problem #2: Iterators
var iterable = {};
iterable[iterator] = function() { /* ... */ };
var iter8tor = iterable[iterator]();
Solution to problem #2: Iterators
var iterable = {};
iterable[iterator] = function() { /* ... */ };
var iter8tor = iterable[iterator]();
iter8tor.next() // -> {value: 'item 1', done: false}
Solution to problem #2: Iterators
var iterable = {};
iterable[iterator] = function() { /* ... */ };
var iter8tor = iterable[iterator]();
iter8tor.next() // -> {value: 'item 1', done: false}
iter8tor.next() // -> {value: 'item 2', done: false}
But there's more…
Generators combine with iterators to allow us to extend the built-in
for…of syntax in powerful ways:
jQuery.prototype[iterator] = function* iterator() {
for (var i = 0; i < this.length; i++)
yield $(this.get(i));
}
for (var p of $('p'))
p.fadeOut();
From @littlecalculist's wiki.
Thanks!
These slides are online at:
aaronj1335 / if-underscore-was-written-in-es6