Javascript

Reference

• JavaScript and HTML DOM reference on w3schools.com

Syntax

JS type

// Strings
var carname = "Volvo XC60";

// Numbers
var x = 3.14;
var y = 34;

JS operators

// Arithmetic operators
x = y + 2;
x = y - 2;
x = y * 2;
x = y / 2;
x = y % 2;       // Modulus (division remainder)
x = ++y;         // Pre-increment
x = y++;         // Post-increment
x = --y;         // Pre-decrement
x = y--;         // Post-decrement

// Assignment operators
x = y;
x += y;
x -= y;
x *= y;
x /= y;
x %= y;

// String operators
text3 = text1 + text2;     // Concatenation
text1 += text2;

// Comparison operators
x == 8;    // equal to
x === 5;   // equal value and equal type
x != 8     // not equal
x !== 5    // not equal value or not equal type
x > 5;
x < 5;
x >= 5;
x <= 5;

// Ternary operator
voteable = (age < 18) ? "Too young" : "Old enough";

// Logical operators
x && y;     // logical and
x || y;     // logical or
!x;         // not

// Bitwise operators
x = 5 & 1;  // bitwise and
x = 5 | 1;  // bitwise or
x = ~5;     // bitwise not
x = 5 ^ 1;  // bitwise xor
x = 5 << 1; // bitwise left shift
x = 5 >> 1; // bitwise right shift

// typeof
typeof "John";            // returns string

// delete
var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};
delete person.age;        // or delete person["age"] -- delete property from an object

// in
var cars = ["Saab", "Volvo", "BMW"];
"length" in cars          // true if property is in the specified object
"firstname" in person

// instanceof
cars instanceof Array;    // true if object is instance of specified class

// void
void(0);                  // evaluate expressions and returns undefined

JS statements

// switch
switch(fruits) {
    case "Banana":
        text = "Banana is good!";
        break;
    default:
        text = "I have never heard of that fruit...";
}

// while
while (i < 5) {
    // ...
}

JS functions

var myfct = function(arg1, arg2) {
     return arg1 + ", " + arg2;
}
myfct("Hello", "World");

Debug

Browser

In Firefox, Ctrl-Shift-C to open up the console and debugger tools.