Javascript

General look on language features

Built-in types

• number
• string
• boolean
• object
• null
• undefined
• symbol (ES6)

...for all properties and methods of built-in types:

MDN is your friend:

https://developer.mozilla.org

Coercion

• Explicit
  •  
• Implicit
  •  

var a = Number('5')

var b = 5 + ''

Truthy and Falsy

Falsy values:

• "" (empty string)
• 0, -0, +0, NaN
• null, undefined
• false

truthy values:

anything except above

Equality

• == (only value)
• === (value and type)
• !=  (only value)
• !== (value and type)

Do not check equality of objects, arrays etc. with ==/===

It doesn't consider their values only reference

Function declaration

Function expression

function doSomething() {
    // ...doing something
}

var doSomething = function () {
    // ...doing something
}

vs

Immediately Invoked Function Expressions (IIFEs)

(function IIFE(){
	var a = 10;
	console.log( a );	// 10
})();


var x = (function IIFE2(){
	return 42;
})();

x;	// 42

"strict mode"

• more optimized code
• prevent auto-global variable
• many more

Details are on next!