Javascript good parts - for novice programmers

JAVASCRIPT - GOOD PARTS
Manohar Shetty || Supriya Anand

SESSION-1
Efforts put in to make a robot called Javascript

SESSION-2
Play with javascipt - alerts, console.logs and what not.

SESSION-2
Frustated! Why somethings work and somethings don't?

GLOBAL VARIABLES
No linker. Global namespace. Variable collisions!
//Your code
function foo() {
if (false) {
var x = 1;
}
return;
var y = 1;
}
//How Javascript interprets it
function foo() {
var x, y;
if (false) {
x = 1;
}
return;
y = 1;
}

'+'
Adds and concatenates.
Un-predictable and error prone
0 + "1"
// returns "01"
"3" + 1
// returns "31"
"3" - "2"
// returns 1

SEMICOLON INSERTION
Semi-colons are INSERTED by the parser
Optional semi-colons are not a “language feature”
You are not warned!! .... 'Uh oh..'
“JavaScript: where forgetting the occasional
semicolon isn't necessarily the end of the
world.”

NOT WHAT YOU EXPECT
TYPEOF()
typeof('abc’) -> string -> Nice
typeof(1) -> number -> Good
typeof({}) -> object -> Great
typeof([1,2,3]) -> object -> Ooops
typeof(null) -> object -> WTH

AGAIN..
== AND !=
‘ ’ == 0 -> false
0 == ‘ ‘ -> true
false == ‘false’ -> false
false == ‘0’ -> true
false == undefined -> false
undefined == null -> true

FLOATING POINTS
0.1 + 0.2 = 0.3 //Nope, back to grade 1 you go!
> 0.1 + 0.2 == 0.3
false
> 0.1 + 0.2 = 0.30000000000000004
WHAT?!

STYLE IS NOT SUBJECTIVE
return {
status: ‘OK’
}
return
{
status: ‘OK’
}
return;
{
status: ‘OK’;
}

OKAY, ENOUGH OF THE BAD!
Show me the good!!

FINALLY, LETS TALK ABOUT THE GOOD.

OBJECT LITERALS
var obj = {
name: 'manohar',
age: 23
}
Pass as options to functions
JSON for communication, remember API's anyone?

DYNAMIC OBJECTS
Members can be added to any object, any time
Helpful to attach attributes
var obj = {
count: 2,
getCount: function(){
return this.count;
}
}
obj.incrementCount = function(){
this.count++;
}
obj.incrementCount();
alert(obj.getCount()); // 3

LOOSELY TYPED
/* JavaScript Example (loose typing) */
var a = 13; // Number declaration
var b = "thirteen"; // String declaration
b=a // b = 13
/* Java Example (strong typing) */
int a = 13; // int declaration
String b = "thirteen"; // String declaration

FUNCTIONS ARE OBJECTS
can be passed, returned
var fibonacci = function(number) {
number < 2 ? number : fibonacci(number -1 ) + fibonacci(number - 2)
}

LAMBDA / CLOSURES
a closure is a reference to the local vars for a function -
local vars kept alive after the function has returned
a closure is a stack-frame which is not deallocated when
the function returns. (as if a 'stack-frame' were malloc'ed
instead of being on the stack!)
function, inner function, outer function, function inside
function, this function, that function
CONFUSED?

CLOSURES, IN ACTION
var wishPeople = function(){
var names = ['manohar', 'supriya', 'hari', 'DP'];
var wish = function(){
for(i=0, n=names.length; i < n;i++) {
console.log("Hello!" + names[i] + ". Welcome to Women Who Code meetup
}
};
return wish;
}();
wishPeople();

Prototypal Inheritance
Memoization
Callbacks
scope
AND MORE!

Javascript good parts - for novice programmers

More Related Content

What's hot

Viewers also liked

Similar to Javascript good parts - for novice programmers

Recently uploaded

Javascript good parts - for novice programmers