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Rob Massicotte - Technical Assessment - Mid-level JavaScript test

by David Lomneck

HTML

<!--don't edit this file-->
<div id=question>
  <span style="font-weight:bold">Question 1:</span> Generate all prime numbers between two given numbers. The two numbers are parameters that can be passed into the function. A prime number is one that is only divisible by 1 and itself. Output the results into the results element below.
  <p>
    Example:
    <br/> Primes between 1 and 10
    <br/> Output:
    <br/> 2
    <br/> 3
    <br/> 5
    <br/> 7
    <br/>
  </p>
</div>
<br/>
<p>Your Results:</p>
<div id="results1"></div>
<br/>
<div id=question>
<span style="font-weight:bold">Question 2:</span> A positive integer is called a palindrome if its representation in the decimal system is the same when read from left to right and from right to left. For a given positive integer K of not more than 1000000 digits, write the value of the smallest
  palindrome larger than K to output. Numbers are always displayed without leading zeros.
  <P>
    Example:
    <br/> Number Given: 808
    <br/> Output: 818
    <br/> Number Given: 2133
    <br/> Output: 2222
    <br/>
  </P>
</div>
<br/>
<p>Your Results:</p>
<div id="results2"></div>
<br/>
<div id="question">
  <span style="font-weight:bold">Question 3:</span> Write a simple string compression algorithm. If a character [ch] occurs n>1 times in a row, then it will be represented by [ch][n].
  <P>
    Example:
    <br/> String Given: aaaa
    <br/> Output: a4
    <br/>
    <br/> String Given: aaabaaaaccaaaaba
    <br/> Output: a3ba4c2a4ba
    <br/>
    <br/> String Given: abcd
    <br/> Output: abcd
    <br/>
  </P>
</div>
<br/>
<p>Your Results:</p>
<div id="results3"></div>
<br/>
<br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>

CSS

p {
  padding: 0px 0px 0px 15px;
}

#question {
  border: 1px solid gray;
}

div {
  padding: 15px 15px 15px 15px;
  border: 1px solid blue;
}

JavaScript

//https://developer.mozilla.org if you need help with syntax
// https://getfirebug.com/firebug-lite-debug.js as external resource for a build-in console window
function Q1(number1, number2) {
  var returnValue = "";
	for (let i = number1 + 1; i < number2; ++i) {
  	if (isPrime(i)) {
    	returnValue += i;
      returnValue += "<br>";
    }
  }
  return returnValue;
}

function isPrime(n) {
	if (n <= 1) {
  	return false;
  }
  
  for (let i = 2; i <= Math.sqrt(n); ++i) {
  	if (n % i == 0) {
    	return false;
    }
  }
  
  return true;
}

function Q2(number1) {
  var returnValue = "";
  var i = number1 + 1;
  
  while (true) {
  	if (isPalindrome(i)) {
    	returnValue += i;
      break;
    }
    
    ++i;
  }
  
  return returnValue;
}

function isPalindrome(num) {
  var str = num.toString();
  var i = 0;
  var j = str.length - 1;
  
  while (i < j) {
  	if (str[i] != str[j]) {
    	return false;
    }
    ++i;
    --j
  }

	return true;
}


function Q3(string1) {
  var returnValue = "";
  var len = string1.length;
	var currentChar = "";
  var currentCharCount = 0;
  
  for (let i = 0; i < len; ++i) {
  	if (string1[i] == currentChar) {
    	++currentCharCount;
      if (i == len - 1) {
      	returnValue += currentChar;
        returnValue += currentCharCount;
      }
    } else {
    	returnValue += currentChar;
      if (currentCharCount > 1) {
      	returnValue += currentCharCount;
      }
    	currentChar = string1[i];
      currentCharCount = 1;
      if (i == len - 1) {
      	returnValue += currentChar;
      }
    }
  }
  
  return returnValue;
}


$("#results1").append(Q1(1, 100));
$("#results2").append(Q2(2133));
$("#results3").append(Q3("a"));