Sebesta Ch 4 Problems

Problem 4.3
Version 0 - no loops

// Start with 'raw code' - no functions.
// Test that we can use prompt by echoing input. ALWAYS
// echo input when testing.
      <script>
	     var first = prompt('enter number','');
	     alert('first = ' + first);
		var second = prompt('enter number','');
	     alert('second = ' + second);
		 var third = prompt('enter number','');
	     alert('third = ' + third);
	  </script>

First solution.  Find a test case for which this does not work.

      <script>
	     var first = prompt('enter number','');
		 var max = first;
		 var second = prompt('enter number','');
		 if(second > max ) max = second;
		 var third = prompt('enter number','');
		 if(third > max) max = third;
		 alert('max = ' + max);
	  </script>

Now, a working version.

      <script>
	     var first = Number(prompt('enter number',''));
		 var max = first;
		 var second = Number(prompt('enter number',''));
		 if(second > max ) max = second;
		 var third = Number(prompt('enter number',''));
		 if(third > max) max = third;
		 alert('max = ' + max);
	  </script>

Package this code in a function. Note that our text says that
function definitions must come before the function is called. 
Some browsers may require this, but I have never encountered it.

      <script>
	  
	  prob43v0();
	  
	  function prob43v0() {
	     var first = Number(prompt('enter number',''));
		 var max = first;
		 var second = Number(prompt('enter number',''));
		 if(second > max ) max = second;
		 var third = Number(prompt('enter number',''));
		 if(third > max) max = third;
		 alert('max = ' + max);
	  }
	  </script>


***********************************************************
Here is a solution to problem 4.3 using arrays
***********************************************************

// Unlike Java, displaying an array shows all the values
// without the need for a loop.

      // Version 1 - array and loop
      function prob43v1() {
         var values = new Array(3);
         for(var index=0; index < 3; index++) {
            values[index] = Number(prompt('enter number',''));
         }
         alert('values = ' + values);
       }

Here is a really irritating feature of JS.  This code
executes without complaint.  What is wrong with it?
      // Version 1 - array and loop
      function prob43v1() {
         var values = new Array(3);
         for(var index=0; index < 3; index++) {
            values[index] = Number(prompt('enter number',''));
         }
         var max = values[0];
		 for(var index = 1; index < 3; index++)
		    if(value[index] > max) max = value[index];
		alsert('max = ' + max);
       }

A corrected version works.

    
      // Version 1 - array and loop
      function prob43v1() {
         var values = new Array(3);
         for(var index=0; index < 3; index++) {
            values[index] = Number(prompt('enter number',''));
         }
         var max = values[0];
		 for(var index = 1; index < 3; index++)
		    if(values[index] > max) max = values[index];
		alert('max = ' + max);
       }

Refactor this code to eliminate the magic number.

      // Version 1 - array and loop
      function prob43v1() {
		 var SIZE = 3;
         var values = new Array(SIZE);
         for(var index=0; index < SIZE; index++) {
            values[index] = Number(prompt('enter number',''));
         }
         var max = values[0];
		 for(var index = 1; index < SIZE; index++)
		    if(values[index] > max) max = values[index];
		alert('max = ' + max);
       }

	   // Version 2 - Math.max
      function prob43v2() {
		 var SIZE = 3;
         var values = new Array(SIZE);
         for(var index=0; index < SIZE; index++) {
            values[index] = Number(prompt('enter number',''));
         }
		 var max = Math.max(values[0],Math.max(values[1],values[2]));
		 alert('max = ' + max);
       }
	   
	  // Version 2a - Math.max - no array
      function prob43v2a() {
		 var SIZE = 3;
		 var max = -999999999;
         for(var index=0; index < SIZE; index++) {
            max = Math.max(max,Number(prompt('enter number','')));
         }
		 alert('max = ' + max);
       }