JavaScript

Two

Recap

HTML+CSS+JS

client-side

data types

string

Objects

Arrays

Functions

==/===

this

Variables

var

Operators

loosely typed

+

expr1 && expr2

Some useful things

window.alert("some message");
document.write("some text");
document.getElementById("testId");
document.getElementsByTagName("divi");
console.log("some text");
innerHTML
window.prompt("some message", "default");

if

            
  if (expression)
    statement

if...else

            
  if (expression)
    statement1
  else
    statement2

else if

            
  if (expression)
    statement1
  else if
    statement2
  else if
    statement3
  else
    statement4

switch

            
  switch (expression)
  {
    case condition 1: statements
                      break;

    case condition 2: statements
                      break;
        ...

    case condition n: statements
                      break;

    default: statements
}

while

          
  while (expression)
    statement

do/while

          
  do
    statement
  while (expression);

for

          
  for(initialize ; test ; increment)
    statement

for/in

          
  for (variable in object)
        statement

loops through the properties of an object

this will also loop through all the properties of all the objects that it inherits from

to loop through the properties of just the current object use:

          
  for (var name in object) {
    if (object.hasOwnProperty(name)) {
      statement
    }
  }

break

causes the innermost enclosing loop or switch statement to exit immediately


            break;

labeled break

to break out of a labeled statement
needs to be nested within the referenced label
labeled statement can be any block statement

          
  outer_block: {
    inner_block: {
      console.log('1');
      break outer_block; // breaks out of both inner_block and outer_block
      console.log('2'); // skipped
    }
    console.log('3'); // skipped
  }

labeled break in loops

put label on a loop and then can break from that loop
useful in case of nested loops

          
  outer: for (var i=0; i<5; ++i){
    console.log("outer: ", i);
    inner: for(var j=0; j<5; ++j){
      console.log("inner: ", j);
      break outer;
    }
  }

if you forget to declare a variable, JavaScript assumes it as a global variable

continue

terminates execution of the statements in the current iteration of the current or labeled loop, and continues execution of the loop with the next iteration

labeled continue

continue statement needs to be nested within this labeled statement

          
  outer: for (var i=0; i<5; ++i){
    console.log("outer: ", i);
    inner: for(var j=0; j<5; ++j){
      console.log("inner: ", j);
      if (j == 2){
        continue outer;
      }
    }
  }

throw

to signal an error or exceptional condition

          
  throw new Error("msg");

          
  throw {name: "exceptionName", message: "msg"};

try/catch/finally

exception handling mechanism

          
  try {
    ...
  }
  catch (e) {
    ...
  }
  finally {
    ...
  }

Creating new objects

with literal notation

          
  var obj = { property_1: value_1, // property_# may be an identifier...
              2: value_2, // or a number...
              // ...,
              "property n": value_n }; // or a string

Creating new objects

using a constructor function

          
  function MyObject(name, type) {
    this.name = name;
    this.type = type;
  }

  var myobj = new MyObject("Test Object", "Test Type");

Creating new objects

using the Object.create() method
creates a new object with the specified prototype object and properties

          
Object.create(proto [, propertiesObject ]);