can one of you javascript experts please help me

I am new to Javascript and have written this script but it is full of errors.
Can someone pleas point them out to me. It would be greatly appreciated
Thank you.
Now here is my script:

<SCRIPT LANGAUGE = "JavaScript">

	function begin();
      		// Initialize calculation type array
	       	var calcType = new Array(5);

	 		for( var arrayCtr = 0; arrayCtr < calcType.length; arrayCtr++ )
				if(arrayCtr = 0)
					calcType[arrayCtr] = "addition";
					if(arrayCtr == 1)
					    calcType[arrayCtr] = "subtraction";
					if(arrayCtr == 2)
						calcType[arrayCtr] = multiplication;
					if(arrayCtr == 3)
						calcType[arrayCtr] = "division";
					if(arrayCtr == 4)
						calcType[arrayCtr] = "modulus";

		// prompt user for calculation type, with the five options specified on the second line displayed
		do {
			var type = window.prompt("Please select the desired operation type:<br>1-Addition, 2-Subtraction, 3-Multiplication, 4-Division, 5-Modulus", "0");
		} while(type > 0 && type < 6);

		   prompt user for the first number, validate that the first character in the string argument is a number,
		   parse the string from left to right until it reaches the end of the number, discard any characters that
		   occur after the end of the number input, and finally return the number as a number (not as a string)

		var num1 = parseInt(window.prompt("Please enter the first number: ", "0"));

		// prompt user for second number, then perform the same conversion as the first number
		var num2 = parseFloat(window.alert("Please enter the second number: ", "0"));


			case 1:
				// call addition function
				var result = add(num1, num2);

			case 2:
				// call subtraction function
				var result = subtract(num 1, num2);

			case 3:
				// call multiplication function
				var result = multiply(num1, num2);

			case 4:
				// call division function
				var result = divide(num1, num2);

			case 5:
				// call mod (remainder) function
				var result = mod(num1, num2);

				window.alert("Invalid operation type")

	// display the results of the calculation in a window alert box
	document.writeln("The result of " + calcType [type] + " is: " + result);


	// addition function definition
	function add(num1, num2){

	   return num1 + num2;


	// subtraction function definition
	function subtract(num1, num2){

	   return num1 - num2;

	// multiplication function definition
	function multiply(num1, num 2){

	   return num1 * num2;

	// division function definition
	function divide(num1, num2){

	   return num1 / num2;


	// modulus (remainder) function definition
	function modulus(num1, num2){

	   return num1 ^ num2;



<BODY ONLOAD = "begin">
<br>Press F1 or click the Refresh (or Reload) button to run this script again</br>
Thank you so so much for any help you can give. thank you