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Edward Lai - 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/>

CSS

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

#question {
  border: 1px solid gray;
}

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

JavaScript

// You may use: 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 = "";

  //Q1 your code here

  return returnValue;
}

function Q2(number1) {
  var returnValue = "";
	
  //Q2 your code here
  var tempNumberString = (number1 + 1).toString().split("").reverse();
  var tempNumber = number1 + 1;
  //var digits = tempNumber.length;
  small = 0;
  big = tempNumberString.length -1;
  
  while ( small <= big) {
  	tempNumberString = (tempNumber).toString().split("").reverse();
		
    if(tempNumberString.length > 1000000 ){
     return "nonexists"
    }

  	if(tempNumberString[small] === tempNumberString[big]){
    	small++;
      big--;
    }
    else if(tempNumberString[small] > tempNumberString[big]){
     tempNumber = Math.floor((tempNumber / 10**(small+1)) + 1)*10**(small+1);
   	  small = 0;
  		big = (tempNumber).toString().length -1;	
    }
    else {
    	tempNumber += 1* 10**(small);
      small = 0;
  		big = (tempNumber).toString().length -1;	
    }
  }
	 
	

  return (tempNumber).toString();//returnValue;
}


function Q3(string1) {
  var returnValue = "";

  //Q3 your code here
  if(string1.length < 1 || !string1) {
  	return "";
  }
  
  let currentChar = string1[0];
  let currentCount = 1;
  
  for(let i=1; i< string1.length; i++) {
  	if(string1[i] !== currentChar) {
    	
      returnValue = returnValue + currentChar + ((currentCount === 1)? "" : currentCount);
      
      currentCount = 1;
      currentChar = string1[i];
    }
    else {
    	currentCount++;
    }
  }

	returnValue = returnValue + currentChar + ((currentCount === 1)? "" : currentCount);

  return returnValue;
}


$("#results1").append(Q1(1, 100));
$("#results2").append(Q2(12211));
$("#results3").append(Q3("abcd"));