CSC 107      Fall 2001

Operator	Name	Data Types	Expressions	Values
+	Addition or Concatenation	Number String	3 + 1 4 + 7.432 "foo" + "bar"	4 11.432 "foobar"
-	Subtraction	Number	7 - 2 5 - 3.359	5 1.641
*	Multiplication	Number	2 * 5 10 * 9.773	10 97.73
/	Division	Number	10 / 4 2.5 / 8	2.5 0.3125
%	Remainder	Number	10 % 4 2 % 0.75	2 0.5
&&	AND	Boolean	true && true true && false false && true false && false	true false false false
||	OR	Boolean	true || true true || false false || true false || false	true true true false
!	NOT	Boolean	!true !false	false true

Comparison:

Operator	Name	Data Types	Examples
==	Equality	Number String Boolean	3 == 3 "test" == "test" false == false
!=	Inequality	Number String Boolean	12 != 39 "foo" != "bar" false != true
<	Less Than	Number String1	2 < 3.1415 "a" < "b"
<=	Less Than or Equal	Number String1	17 <= 17 "ABC" <= "ABD"
>	Greater Than	Number String1	12 > -4 "foo" > "bar"
>=	Greater Than or Equal	Number String1	3.99 >= 3.98 "fool" >= "foo"
1. Strings follow standard dictionary ordering, i.e.,     "A" < "B" < ... < "Z" < "a" < "b" ... < "z"     "a" < "aa" < ... < "ab" < "aba" < ... < "b"

Statements:

Statement Name	General Form	Examples
Comment	// Comment... /* Comment... */	// A one line comment. /* A comment that goes onto more than one line */
Assignment Statement	variable = expression; variable: sequence of letters, digits, and underscores that starts with a letter. expression: either a simple value (number, string, or boolean) or else operators applied to values. The value of the expression on the right-hand side is assigned to the variable on the left-hand side.	x = 7.5; FirstName = "Dave"; flag = true; prod2to4 = 2 * 3 * 4; // assigns value 24 y = (x + 1) * 3; // assigns value 25.5 hi_message = "Hello " + FirstName; // assigns value "Hello Dave" BOOL = true && !false; // assigns value true
If-Then Statement	if (test) { if-clause } else { else-clause } test: Evaluates to true or false. if-clause: Executed if test==true. else-clause: Executed if test==false. The else-clause is optional.	if (x >= 0) { x = x + 3; } if (x < 0) { x = x - 1; } else { x = x + 1; }
While Loop	while (test) { loop-body } test: Evaluates to true or false. If test==true the loop body is executed and the test is performed again.	sum = 0; while (x >= 1) { sum = sum + x; x = x - 1; } count = 1; while (count <= 10) { document.write("foo<BR>"); count = count + 1; }

Built In Functions:

Function	Examples	Result
Square Root	x = Math.sqrt(9);	x == 3
Absolute Value	x = Math.abs(-23); y = Math.abs(99);	x == 23 y == 99
Maximum	x = Math.max(3,14);	x == 14
Minimum	x = Math.min(3,14);	x == 3
Power	x = Math.pow(2,3);	x == 8
Floor	x = Math.floor(3.14159); y = Math.floor(4.5623);	x == 3 y == 4
Ceiling	x = Math.ceil(3.14159); y = Math.ceil(4.5623);	x == 4 y == 5
Round	x = Math.round(3.14159); y = Math.round(4.5623);	x == 3 y == 5
ParseFloat	x = parseFloat("12.8"); y = parseFloat("ABC");	x == 12.8 y == NaN
Prompt	yourName = prompt("Please enter your name","Anonymous"); The following dialog box will appear, and yourName will be assigned the value that is entered in the text field.
Write	document.write("Howdy"); document.write(2+3);	displays "Howdy" displays 5

User Defined Functions

Action	General Form	Examples
Function Definition	function FuncName(param1, param2,...) { variable-declarations function-body return return-value; } FuncName: The name of the function. param1: The name of the first parameter passed to the function. variable-declarations: list of local variables (if any) that appear in the function, preceded by var. function-body: JavaScript statements to be executed when the function is called. return-value: Value that is returned from this function. The return statement is optional.	function FooFunc() // Returns: the string "foo" { return "foo"; } function BarFunc(N) // Assumes: N >= 0 // Returns: string of N "bar"s { var theStr; theStr = ""; while (N > 0) { theStr = theStr+"bar"; N = N - 1; } return theStr; } function Greet(name) // Assumes: name is a string // Results: displays greeting { document.write("Hi "+name); }
Function Call	myVar = FuncName(arg1, arg2,...); myVar: Variable to hold the value (if any) returned by the function. FuncName: Name of the function to call. arg1: Argument 1, the value for the first parameter of the function.	Str1 = FooFunc(); // Result: Str1 == "foo" Str2 = BarFunc(3); // Result: Str2 == "barbarbar" Greet("Dave"); // Result: displays "Hi Dave"