Splice to add, replace and remove javascript array

Here is working code link : http://plnkr.co/edit/SHfpFQ?p=preview

Splice is an effective way to add, replace or remove elements from specific index in Javascript Array.

Javascript array splice() method changes the content of an array, adding new elements while removing old elements.

Syntax

Its syntax is as follows −

array.splice(index, howMany, [element1][, ..., elementN]);

Parameter Details

  • index − Index at which to start changing the array.
  • howMany − An integer indicating the number of old array elements to remove. IfhowMany is 0, no elements are removed.
  • element1, …, elementN − The elements to add to the array. If you don’t specify any elements, splice simply removes the elements from the array.

Return Value

Returns the extracted array based on the passed parameters.

If you specify a different number of elements to insert than the number you’re removing, the array will have a different length at the end of the call.

Examples

Using splice()

The following script illustrates the use of splice():

var myFish = ['angel', 'clown', 'mandarin', 'surgeon'];

// removes 0 elements from index 2, and inserts 'drum'
var removed = myFish.splice(2, 0, 'drum');
// myFish is ['angel', 'clown', 'drum', 'mandarin', 'surgeon']
// removed is [], no elements removed

// removes 1 element from index 3
removed = myFish.splice(3, 1);
// myFish is ['angel', 'clown', 'drum', 'surgeon']
// removed is ['mandarin']

// removes 1 element from index 2, and inserts 'trumpet'
removed = myFish.splice(2, 1, 'trumpet');
// myFish is ['angel', 'clown', 'trumpet', 'surgeon']
// removed is ['drum']

// removes 2 elements from index 0, and inserts 'parrot', 'anemone' and 'blue'
removed = myFish.splice(0, 2, 'parrot', 'anemone', 'blue');
// myFish is ['parrot', 'anemone', 'blue', 'trumpet', 'surgeon']
// removed is ['angel', 'clown']

// removes 2 elements from index 3
removed = myFish.splice(3, Number.MAX_VALUE);
// myFish is ['parrot', 'anemone', 'blue']
// removed is ['trumpet', 'surgeon']

codeschool.com–A nice site to learn advanced frameworks like Angular JS

This is the era of eLearning. By virtue of eLearning you can avail the best instructor with nice and interactive training material and too at the time and pace you like. Today I completed an Angular course which I like to recommend you in case if you want to learn things in an interactive way.

https://www.codeschool.com/courses/shaping-up-with-angular-js 

The course is hands on course with challenges, hints and tutorial videos which are both verbal explanation with technical code walk through. Course is divided in modules and levels of challenges to track the progress.

Try it Winking smile 

angular

JS : What is JavaScript ?

JavaScript (JS) is an interpreted computer programming language. It was originally implemented as part of web browsers so that client-side scripts may interact with the user, control the browser, communicate asynchronously and alter the document content that is displayed.
JavaScript is prototype-based scripting language that is dynamic, weakly typed and has first-class functions.
It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles.
 
Features

Imperative and structured
JavaScript supports much of the structured programming syntax from C (e.g., if statements, while loops, switch statements, etc.). One partial exception is scoping: C-style block-level scoping is not supported (instead, JavaScript has function-level scoping). JavaScript 1.7, however, supports block-level scoping with the let keyword. Like C, JavaScript makes a distinction between expressions and statements. One syntactic difference from C is automatic semicolon insertion, in which the semicolons that terminate statements can be omitted.

Dynamic
dynamic typing
As in most scripting languages, types are associated with values, not with variables. For example, a variable x could be bound to a number, then later rebound to a string. JavaScript supports various ways to test the type of an object, including duck typing.[25]
object based
JavaScript is almost entirely object-based. JavaScript objects are associative arrays, augmented with prototypes (see below). Object property names are string keys: obj.x = 10 and obj[‘x’] = 10 are equivalent, the dot notation being syntactic sugar. Properties and their values can be added, changed, or deleted at run-time. Most properties of an object (and those on its prototype inheritance chain) can be enumerated using a for…in loop. JavaScript has a small number of built-in objects such as Function and Date.
run-time evaluation
JavaScript includes an eval function that can execute statements provided as strings at run-time.

Functional
first-class functions
Functions are first-class; they are objects themselves. As such, they have properties and methods, such as .call() and .bind(); and they can be assigned to variables, passed as arguments, returned by other functions, and manipulated like any other object. Any reference to a function allows it to be invoked using the () operator.
nested functions and closures
“Inner” or “nested” functions are functions defined within another function. They are created each time the outer function is invoked. In addition to that, each created function forms a lexical closure: the lexical scope of the outer function, including any constants, local variables and argument values, become part of the internal state of each inner function object, even after execution of the outer function concludes.
Prototype-based

prototypes
JavaScript uses prototypes instead of classes for inheritance. It is possible to simulate many class-based features with prototypes in JavaScript.
functions as object constructors
Functions double as object constructors along with their typical role. Prefixing a function call with new creates a new object and calls that function with its local this keyword bound to that object for that invocation. The constructor’s prototype property determines the object used for the new object’s internal prototype. JavaScript’s built-in constructors, such as Array, also have prototypes that can be modified.
functions as methods
Unlike many object-oriented languages, there is no distinction between a function definition and a method definition. Rather, the distinction occurs during function calling; a function can be called as a method. When a function is called as a method of an object, the function’s local this keyword is bound to that object for that invocation.

Miscellaneous
run-time environment
JavaScript typically relies on a run-time environment (e.g. in a web browser) to provide objects and methods by which scripts can interact with “the outside world”. In fact, it relies on the environment to provide the ability to includeimport scripts (e.g. HTML <script> elements). (This is not a language feature per se, but it is common in most JavaScript implementations.)
variadic functions
An indefinite number of parameters can be passed to a function. The function can access them through formal parameters and also through the local arguments object.
array and object literals
Like many scripting languages, arrays and objects (associative arrays in other languages) can each be created with a succinct shortcut syntax. In fact, these literals form the basis of the JSON data format.
regular expressions
JavaScript also supports regular expressions in a manner similar to Perl, which provide a concise and powerful syntax for text manipulation that is more sophisticated than the built-in string functions.

JS : What are global variables in JavaScript

Global variables are available throughout your code: that is, the variables have no scope. Local variables scope, on the other hand, is restricted to where it is declared (like within a function). The var keyword is used to declare a local variable or object, while omitting the var keyword creates a global variable.

Most JavaScript developers avoid globals. One reason why is they’re averse to naming conflicts between local and globals, Also, code that depends on globals can be difficult to maintain and test.

// Declare a local variable
var localVariable = "sessionId"
// Declare a global
globalVariable = “daatabaseURL"

Javascript : What is event propogation

Event Propagation

 

When a click occurs on a DOM element, the element notifies its parent, who then notifies his parent, and so on. This event propagates through the DOM until it gets to the document object. Lets say you clicked on anchor link which is inside a P tag, which is inside Div tag , finally which is inside the html body = DOM

The basic problem is very simple. Suppose you have a element inside an element

-----------------------------------
| element1 (div)                  |
|   -------------------------     |
|   |element2 (span)              |     
|   -------------------------     |
|                                 |
-----------------------------------

and both have an onClick event handler. If the user clicks on element2 he causes a click event in both element1 and element2. But which event fires first? Which event handler should be executed first? What, in other words, is the event order?

Two models

Not surprisingly, back in the bad old days Netscape and Microsoft came to different conclusions.

  • Netscape said that the event on element1 takes place first. This is called event capturing.
  • Microsoft maintained that the event on element2 takes precedence. This is called event bubbling.

The two event orders are radically opposed. Explorer only supports event bubbling. Mozilla, Opera 7 and Konqueror support both.

Event capturing

When you use event capturing

               | |
---------------| |-----------------
| element1     | |                |
|   -----------| |-----------     |
|   |element2  \ /          |     |
|   -------------------------     |
|        Event CAPTURING          |
-----------------------------------

the event handler of element1 fires first, the event handler of element2 fires last.

Event bubbling

When you use event bubbling

               / \
---------------| |-----------------
| element1     | |                |
|   -----------| |-----------     |
|   |element2  | |          |     |
|   -------------------------     |
|        Event BUBBLING           |
-----------------------------------

the event handler of element2 fires first, the event handler of element1 fires last.

The web developer, can choose whether to register an event handler in the capturing or in the bubbling phase. This is done through the addEventListener() method. If its last argument is true the event handler is set for the capturing phase, if it is false the event handler is set for the bubbling phase.

W3C model

W3C has very sensibly decided to take a middle position in this struggle. Any event taking place in the W3C event model is first captured until it reaches the target element and then bubbles up again.

                 | |  / \
-----------------| |--| |-----------------
| element1       | |  | |                |
|   -------------| |--| |-----------     |
|   |element2    \ /  | |          |     |
|   --------------------------------     |
|        W3C event model                 |
------------------------------------------

You, the web developer, can choose whether to register an event handler in the capturing or in the bubbling phase. This is done through the addEventListener() method. If its last argument is true the event handler is set for the capturing phase, if it is false the event handler is set for the bubbling phase.

Suppose you do

element1.addEventListener('click',doSomething2,true)
element2.addEventListener('click',doSomething,false)

If the user clicks on element2 the following happens:

  1. The click event starts in the capturing phase. The event looks if any ancestor element of element2 has a onclick event handler for the capturing phase.
  2. The event finds one on element1. doSomething2() is executed.
  3. The event travels down to the target itself, no more event handlers for the capturing phase are found. The event moves to its bubbling phase and executes doSomething(), which is registered to element2 for the bubbling phase.
  4. The event travels upwards again and checks if any ancestor element of the target has an event handler for the bubbling phase. This is not the case, so nothing happens.

The reverse would be

element1.addEventListener('click',doSomething2,false)
element2.addEventListener('click',doSomething,false)

Now if the user clicks on element2 the following happens:

  1. The click event starts in the capturing phase. The event looks if any ancestor element of element2 has a onclick event handler for the capturing phase and doesn’t find any.
  2. The event travels down to the target itself. The event moves to its bubbling phase and executes doSomething(), which is registered to element2 for the bubbling phase.
  3. The event travels upwards again and checks if any ancestor element of the target has an event handler for the bubbling phase.
  4. The event finds one on element1. Now doSomething2() is executed.

 

 

 

 

Javascript: Changing Class Names Issue on IE

IE has issue to change the class of an element using java scrip
   var currentTag = document.getElementById(tagID);
   currentTag.setAttribute("class", "stlyeclass");
this does not work on IE and the work around for the same is
use setAttribute("className", "stlyeclass") instead of setAttribute("class", "stlyeclass");
But funny thing is that it will stop working on fire fox. So to make code cross browser use both some thing demonstrated below:

function changeCSS(tagID)
{
   var currentTag = document.getElementById(tagID);
   currentTag.setAttribute("class", "secondClass");
   currentTag.setAttribute("className", "secondClass");
   return;
}