Syntax

JavaScript Syntax

• Statements
• Variables
• Arrays
• Functions
• Objects

Statements

Separate lines:

Statement 1
Statement 2

Separated by semi-colons:

Statement 1;Statement 2

Both:

Statement 1;
Statement 2;

Comments

A statement that isn't executed.

Statement 1;
// comment
Statement 2;

Variables

A label that stands for a value, even if the value changes.

Numbers, strings, Boolean values:

var age = 34;
var name = "Jeremy";
var name = 'Jeremy';
var height = '5\'10"';
var male = true;

Variables

JavaScript is a weakly typed language

var foo = 37.5;
var foo = "bar";

Arrays

A variable that is a collection of variables.

var fruit = new Array();
fruit[0] = "apple";
fruit[1] = "orange";
fruit[2] = "banana";

Combine declaring and setting:

var fruit = new Array("apple","orange","banana");

Arrays

The length of an array.

var fruit = new Array("apple","orange","banana");
alert(fruit.length);

Alert: 3

Arrays

var fruit = new Array("apple","orange","banana");
alert(fruit[0]);

Alert: apple

Arrays

for (initial condition; test condition; change operation)

var fruit = new Array("apple","orange","banana");

for (var i=0; i<fruit.length; i++) {
  alert(fruit[i]);
}

Alert: apple

Alert: orange

Alert: banana

Functions

A self-contained series of statements

function functionName (arguments) {
  Statements;
}

Functions

function multiply(x,y) {
  var result = x * y;
  return result;
}

var mynum = multiply(2,6);
alert(mynum);

Alert: 12

Variable scope

• Global
• Local (var)

function multiply(x,y) {
  var result = x * y;
  return result;
}

Variable scope

function multiply(x,y) {
  result = x * y;
  return result;
}

result = 10;

var mynum = multiply(2,6);

alert(mynum);

alert(result);

Alert: 12

Alert: 12

Objects

Self-contained bundles of functions and variations.

• A variable that belongs to an object is a property.
• A function that belongs to an object is a method.

Dot syntax:

object.property
object.method()

Objects

• Native objects
• Host objects
• User-defined objects

Native objects

The Math object

Math.round(3.14);

The round method of the Math object.

Native objects

The Array object

Array.length;

The length property of the Array object.

Host objects

The window object

window.open("http://www.example.com/");

The open method of the window object.

Next...

The document object

Methods and properties of the document object...