The Tor Browser / file revision

 /*

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/

  */

 // Some simple testing of new, eval and some string stuff.

 // constructor -- expression array initialization

 function ExprArray(n,v)

 {

     // Initializes n values to v coerced to a string.

     for (var i = 0; i < n; i++) {

 	this[i] = "" + v;

     }

 }

 // Print the perfect numbers up to n and the sum expression for n's divisors.

 function perfect(n)

 {

     print("The perfect numbers up to " +  n + " are:");

     var results = [];

     // We build sumOfDivisors[i] to hold a string expression for

     // the sum of the divisors of i, excluding i itself.

     var sumOfDivisors = new ExprArray(n+1,1);

     for (var divisor = 2; divisor <= n; divisor++) {

 	for (var j = divisor + divisor; j <= n; j += divisor) {

 	    sumOfDivisors[j] += " + " + divisor;

 	}

 	// At this point everything up to 'divisor' has its sumOfDivisors

 	// expression calculated, so we can determine whether it's perfect

 	// already by evaluating.

 	if (eval(sumOfDivisors[divisor]) == divisor) {

 	    print("" + divisor + " = " + sumOfDivisors[divisor]);

 	    results.push(divisor);

 	}

     }

     print("That's all.");

     return results;

 }

 print("\nA number is 'perfect' if it is equal to the sum of its")

 print("divisors (excluding itself).\n");

 reportCompare(perfect(500).join(), "6,28,496");