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

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.

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;
}

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)
	}
}

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