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@mattbaker
Last active August 29, 2015 13:55
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"Wealthfront-style" Option Monad using ES6 Iterators
/*
* A Wealthfront-style Option implementation in Javascript implementing ES6 iterables
* Reference:
* http://eng.wealthfront.com/2010/05/better-option-for-java.html
*
* This only runs in current versions of Firefox.
* It's recommended you use the FF Scratchpad with the web console open to see logging results:
* https://developer.mozilla.org/en-US/docs/Tools/Scratchpad
*/
function Option(v) {
this.v = v;
}
Option.prototype.__iterator__ = function(){
return new OptionIterator(this);
};
Option.of = function (v) {
return new Option(v);
}
function OptionIterator(option) {
this.option = option;
this.accessed = false;
}
OptionIterator.prototype.next = function() {
if (this.accessed || this.option.v === null) {
throw StopIteration;
}
this.accessed = true;
return this.option.v;
}
var maybeThereButIsnt = Option.of(null);
var maybeThereAndIs = Option.of(20);
for(var value in maybeThereButIsnt) {
console.log("I'm not here! " + value);
}
for(var value in maybeThereAndIs) {
console.log("I'm here! " + value);
}
/*
* Console Output:
*
* > "I'm here! 20"
*
*/
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