A JavaScript function for converting a number from decimal to binary.

decimalToBinary.js

/*********************************************************
 *  Converts a positive integer from decimal to binary.
 *  @param {Number} decimalNumber (e.g. 5)
 *  @return {Number} binaryNumber (e.g. 101)
 ********************************************************/
 function decimalToBinary( decimalNumber ) {
  
   // binaryNumber represents a summation of digit values.
   var binaryNumber = 0;
   
   // placeValue represents a power of ten.
   var placeValue = 1;
   
   // Compute each digit value (from right to left). 
   while ( decimalNumber > 0 ) {
    
     // Divide decimalNumber by 2. Store the binary remainder.
     var remainder = decimalNumber % 2;
     
     // Determine the remainder digit.
     var digitValue = remainder * placeValue;

     // Add the digitValue to the binaryNumber sum.
     binaryNumber += digitValue;

     // Increment the placeValue.
     placeValue *= 10;

     // Increment to the next digit (left adjacent).
     decimalNumber = Math.floor( decimalNumber / 2 );
   }

   // Return the sum of digit values.
   return binaryNumber;
 }