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# Imperative vs. Recursive vs. Functional [ Work-in-progress ]

``````// Imperative: The Fastest ( + very simple, no new pointers or excess allocs ):
function fib(n) {
var a = 1, b = 1, c = 0;
for(var i = 1; i < n-1; ++i) {
c = a + b;
a = b;
b = c;
}
return b;
}

// Recursive: (FIREFOX or BABELJS Only) ES6 function definition with
//  parameter defaults used to set initial (internal/recursive) values
function fib(n, current=0, a=1, b=1, c=0) {
current++;
c = a + b;
a = b;
b = c;
return current >= n ? b : fib(n, current, a, b, c);
}

// Text-book-Bad Example - poor function scope w/ multiple mutable external values
function fib(n) {
if (!arr) { var arr = [1,1]; n=n-2; };// Bad
if (n===-1) {return [arr];}
if (n===0) {return arr;}
var proc = function() {
--n;
arr.push(arr[arr.length-1] + arr[arr.length-2]);
return (n===0 ? arr : proc());
// Bad: inner recursive function not needed, hint: variables used are from parent function scope
};
var ans = proc();
return ans[ans.length-1];
}``````

# Promises: Awesome!

``````// Example Using bluebird Promises and it's
var Promise = require('bluebird'),
fs = Promise.promisifyAll(require('fs')),
less = Promise.promisifyAll(require('less'));

function writeFileData(data) {
return fs.writeFileAsync('/tmp/output.css', data);
}
// Bluebird makes something like this perhaps uncomfortably simple and succinct:
.then(less.renderAsync)         // Hand off to less.render
.then(writeFileData);      // Function to recieve the css contents (1st parameter)``````
1. While, native ES6 Promises are great, I prefer the robust Bluebird Promise Library.
2. Library or not, modern browsers have supported Promise for years.
3. Promises can be utilized without crazy patterns - implicit `deferred` is preferable.
4. \$q just sucks just use bluebird, see above.
5. Worth mentioning: Bluebirds Benchmarks are best-case tests, so take note if doing crazy fancy promise chains

# Java vs JavaScript

## Rate Limiting / Debouncing / Throttling

1. In JavaScript David Walsh implemented debounce in less than 20 lines!
2. In Java, JDebounce, an library which is a lot more complicated, at ~500+ lines.
3. _ Comparing the two: _
4. The JavaScript is fast & uses first-class functions to achieve brilliant simplicity.
5. Whereas the Java has many more moving parts, annotations are used to apply behaviour at compile-time, and there’s a ton of XML, just for funsies!