Javascript for the c# developer

JavaScript forC# Devs
Salvatore Di Fazio – MVP SharePoint Server
http://salvatoredifaziosharepoint.blogspot.co.uk
Twitter: @Salvodif

Why aJS session
if we speak about
SharePoint?
• Sharepoint 2013 – Javascript & jQuery big booboo to watch out
for: http://alturl.com/3xdvz
• “so everyone likes jQuery right? Even Microsoft like it, even the
SharePoint team like it. Unfortunately, 99.999% of the code you see
out there using jQuery makes a big huge mistake. And that is, to
load the $ variable in the global namespace…”
• Web 2.0 – when a client ask for a new feature, most of the
time, the comparison is one of the new social network
(Facebook,Twitter, Instagram,Yammer, etc.)
• Microsoft is pushing

Improvement
fromSharePoint
2007 to
SharePoint 2013
JavaScriptAPI for
Office

starter
• JavaScript is object based, everything is an object
• Variables created using var
• You should always use semicolons, and an object is a collection of
name/value
name: value
• JavaScript is case sensitive
• Always use strict mode, declared with use strict
• Cannot use a variable without declaring it
• Cannot define a property more than once in an object literal
• Cannot use a parameter name more than once in a function
• Cannot use reserved words
• The value of this in a function is no longer the window object
• Cannot change the members of the arguments array
• Etc...

Functions
 Start with the keyword function
 Can have a name or not
 Can have parameters or not, by default exist the arguments
param
 The delimiters of the function are { }
 A function can return a value, and that value can be itself
 Cannot be overloaded!!!
 Parameters not passed are setted undefined
 Is possible to have a function inside a function Closure
 Functions have this and it identify the current context
 Every function has a property named prototype

Null
and
undefined
• NULL
• Primitive types
• Represents the absence of value
• Evaluates to false in Boolean expressions
• UNDEFINED
• Primitive type
• Represents an unknown value
• Returned when a non-existent object property is called
• Evaluates to false in Boolean expressions

Avoid coercive
equality operators
 Objects are only equal to themselves
 Primitives are equal if the values match (“salvo” === “salvo”)
 Two sets of equality operators ( == and ===)
 never use == or != INSTEAD of === or !==
0 == '0'; //true
0 === '0'; //false
false == '0'; //true
false === '0'; //false

 Global scope
 Comparision == OR ===
 Prototype
DEMO

Classes
 We create a class in JS by a pattern:
 Using function, the most common ways
 Using object literals
 Singleton using a function
 Use it to prevent name collisions and polluting parent namespace
 Use the new keyword to invoke the constructor
 Use the prototype to expand it:
 Using it avoid to recreated every time the method when the
constructor is invoked, using the prototype avoid this effort

Closure
Whenever you see the function keyword within another
function, the inner function has access to variables of the outer
function
http://stackoverflow.com/questions/111102/how-do-javascript-
closures-work

Module
 The window object in browsers is a global namespace
 Variables defined outside a function are in the global namespace
 Variables defined without the var keyword are in the global namespace
 Always create your own namespace by a pattern
 The module pattern was made by Eric Miraglia ofYUI in the 2007
 Use it to prevent name collisions and polluting parent namespace
 Keep everything tidy
 Module Export Pattern:
var MODULE = (function () {
var my = {},
privateVariable = 1;
function privateMethod() {
// ...
}
my.moduleProperty = 1;
my.moduleMethod = function () {
// ...
};
return my;
}());
 AnonymousClosures Pattern:
(function () {
// ... all vars and functions are in this scope only
// still maintains access to all globals
}());

Some useful links• Strict Mode - http://msdn.microsoft.com/en-us/library/ie/br230269(v=vs.94).aspx
• Strict Mode - http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
• JavaScript info - https://developer.mozilla.org/en-US/docs/JavaScript/Reference/
• Namespace function -
https://github.com/smith/namespacedotjs/blob/master/example/sandbox.js
• TypeScript

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