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javascript Closure IIFE Immediately Invoked Function

Javascript Closure

This is an example of how to use iffe closure example to avoid collisions with other global variables in your programs. By placing the variable in the function it makes it private and not accessible everywhere else that would create a problem.

// global variable bad because of collisions
// break other programs avoid globals
var names = ['zero', 'one', 'two', 'three', 'four', 'five'];

var digit_name = function (n) {
	return names[n];
}

console.log(digit_name(3)) // 'three'

// SLOW - because we have to create an variable array every time you try invoking it.
// prevents collision of global variables - names
var digit_name = function (n) {
	var names = ['zero', 'one', 'two', 'three', 'four', 'five'];
	return names[n];
}

console.log(digit_name(3)) // 'three'

// closure iife - immediate invoked function 
// it executes the function has access to the variable names in the iffy
var digit_name = (function () {
	var names = ['zero', 'one', 'two', 'three', 'four', 'five'];
	return function (n) {
		return names[n];
	}
})();

console.log(digit_name(3)) // 'three'

 

The third way to do this is the best. To avoid collisions.

Power Constructors

  1. Make an object
    • Object Lateral
    • new
    • Object.create
    • call another power constructor
  2. Define some some variables and functions
    • These become private members
  3. Augment the object with privileged methods.
  4. Return the object
function myPowerConstructor(x) {
	var that = otherMaker(x);
	var secret = f(x);
	that.priv = function () {
		//secret x that
	};
	return that;
}

 

Functional Inheritance

function gizmo(id) {
	return {
		id: id,
		toString: function () {
			return "gizmo " + this.id;
		}
	};
}

function hoozit(id) {
	var that = gizmo(id);
	that.test = function (testid) {
		return testid === this.id;
	};
	return that;
}

Source:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
https://en.wikipedia.org/wiki/Immediately-invoked_function_expression

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How to Setup Your Own Parse Server

Since you already have heard that parse is closing down. Here are some instruction to set up you own parse. You can read more about the announcement here. You Can set up Parse with heroku or AWS.

The guides are at:

Heroku: https://devcenter.heroku.com/articles/deploying-a-parse-server-to-heroku

AWS: http://mobile.awsblog.com/post/TxCD57GZLM2JR/How-to-set-up-Parse-Server-on-AWS-using-AWS-Elastic-Beanstalk

If you’re not sure which to choose I’d go for Heroku as the process is a fair bit more straightforward.

Happy Coding. Now you have your own backend.

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Javascript – How to Create Functions to replace text, factorial, check if it’s even

These are some code snippets on how to create functions to check if a number is even. Do a factorial with a for loop. Do a text replacement with regular expressions.

// isEven f(x)
function isEven(arg) {
	return arg%2 === 0
}
// factorial f(x)
function factorial(num) {
	var result = 1;
	for(var i = 2; i <= num; i++) {
		result = result * i;
	}
	return result;
}
// kebabToSnake() Replace a string "-" with '_'s
function kebabToSnake(str) {
	var newStr = str.replace(/-/g , "_");
	return newStr;
}
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Javascript – Simple For Loop Examples

These are some examples of simple for loop challenges and exercises I did for fun.

// Print 'hello' the string vertically
var str = 'hello';
for(var count = 0; count < str.length; count++) {
	console.log(str[i])
}
// print all numbers between -10 and 19

for(var i = -10; i < 20; i++) {
	console.log(i)
}

// print even numbers between 10 and 40

for(var i = 10; i < 40; i++) {
	if(i % 2 === 0){
	console.log(i)
	}
}
// print all odd numbers between 300 and 333
for(var i = 300; i < 333; i++) {
	if(i % 3 === 0){
	console.log(i)
	}
}
// print all numbers divisible by 5 and 3 between 5 and 50
for(var i = 5; i < 50; i++)	{
	if(i % 3 === 0 && i % 5 === 0) {
	console.log(i)
	}
}
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Javascript can be dynamically typed – Array Example

This is code example of javascript being dynamically typed with arrays. Arrays can store, anything: strings, objects, functions, strings, and integers. Below is example how to call an object lateral and function. Remember arrays start count at 0.

var arr = [1,
           2,
           3,
           {
           name: 'jason',
             addy: '111 fake st'
           },
           function(name){
           	var greeting = 'hello ';
             console.log(greeting + name);
           },
           'hello'
          ];
arr[4](arr[3].name);

// hello jason
Posted on

How to Setup Babel es2015 Javascript on Windows 8.1?

First create a folder:
Then CD into that folder through CMD
Then do the follow in command-line

npm init
npm install -g babel-cli
npm install babel-preset-es2015–save-dev

Then create app.js.es6 file

Then use this example code:

class Person {
	constructor(name) {
		this.name = name;
	}
	greet(){
		return "Hello I am ${this.name}";
	}
}

let person = new Person("Tyler");
console.log(person.greet());

babel app.js.es6 –presets2015 | clip

Clip copies the string from commandline. Then you should get the follow code output:

"use strict";

var _createClass = (function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Person = (function () {
	function Person(name) {
		_classCallCheck(this, Person);

		this.name = name;
	}

	_createClass(Person, [{
		key: "greet",
		value: function greet() {
			return "Hello I am ${this.name}";
		}
	}]);

	return Person;
})();

var person = new Person("Tyler");
console.log(person.greet());

Now we want to create an index.html file

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>
</head>
<body>
	<h2>ES2015</h2>

	<script src="app.js"></script>
</body>
</html>

babel app.js.es6 –presets es2015 > 5

Now we are going to create a file called .bablrc this file will shorten the command to compile the babel file

{
	presets: ["es2015"]
}

Next we type in this code to make compiling es2015 javascript faster.

babel app.js.es6 > app.js

babel_CMD_setup

https://github.com/JasonDeving/babel2015windowssetup

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javascript – namespacing, public and private data

This is quick code sample of public and private data using javascript. You would create anonymous call back function. Private data would be store in var.
Public data would be returned.

// we create anonymous callback function to create private and public functions
var THINGS = function() {
// private
var gifts = 3;
// public
return {
    gems: 1000,
    gold: 2000,
    swords: 300,
    SECRET: {
      open: function() {
        gifts--;
        alert('OPENED!');
      }
    }
};}();

I hope you found this code snippet useful in your coding. These are higher order examples of code has to deal with object orientated programming. You can apply these concepts elsewhere.

Public functions can be access and changed anywhere. Where as private can’t be changed the numbers stay static. For example gifts will stay 3, but the public function can subtract it in increments of negative 1.

The reason behind public and private is track bugs. If you have too many public/global variables you get lost quick and other variables can overwrite those current variables, which is something you don’t want. Plus there is name spacing here the namespace is THINGS.

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Javascript – Sales Tax Program

function tax (price, percent) {
		return parseFloat((price*percent/100).toFixed(2));
	}
	var randomItem = 9.85;
	var salesTax = 7.5;
	var total = randomItem + tax(randomItem, salesTax);
	console.log(total);

 

This is a program on how to calculate sales tax with javascript, because handling floats is a bit weird with javascript.

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How to Benchmark Your Javascript?

This is a quick tutorial on how to benchmark your javascript with console.time(“arg”) and console.timeEnd(“arg”)
You would use developer tools to see how fast your script runs.
javascript_benchmark

Example Code:

Array.prototype.proto1 = function(){};
Array.prototype.proto2 = function(){};
Array.prototype.proto3 = function(){};
Array.prototype.proto4 = function(){};
Array.prototype.proto5 = function(){};

var objectLateral = {
  arrayBank: ['Some random string', 'Other String', 'More Stringy Spaghetti']
};

function runThisCode(){
  var things = objectLateral.arrayBank,
      list = "";
	console.time("time");  

  for(var i = 0, ff = things.length; i < ff; i++){
    list += (things[i] + " ");
  }

  console.timeEnd("time");
  return list.trim();
}

runThisCode();