/index.html

## index.html
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

<script id="jsbin-javascript">
function findDiff(original, newText) {

  function getZip(originalList, newTextList){
    return originalList.map(function(char,i) {
      return {
        first: char,
        second: newTextList[i]
      }
    })
  }

  function findDiffPoint(zippedList) {
    var start = 0
    zippedList.forEach(function(pair, index) {
      if (start > 0) return
      if (pair.first != pair.second) {
        start = index
      }
    })
    return start
  }

  var zip = getZip(
    original.split(''),
    newText.split('')
  )
  var diffStart = findDiffPoint(zip)
  var reverseZip = getZip(
    original.split('').reverse(),
    newText.split('').reverse()
  )

  var diffEnd = newText.length - findDiffPoint(reverseZip)

  var added = newText.slice(diffStart,diffEnd)

  return {
    start: diffStart,
    end: diffEnd,
    added: added
  }
}


var original = "first para\n Second para"
var newText =  "first para\n <b> INSERT </b> Second para"

diff = findDiff(original,newText)
console.log(
  diff
)
</script>


<script id="jsbin-source-javascript" type="text/javascript">function findDiff(original, newText) {

  function getZip(originalList, newTextList){
    return originalList.map(function(char,i) {
      return {
        first: char,
        second: newTextList[i]
      }
    })
  }

  function findDiffPoint(zippedList) {
    var start = 0
    zippedList.forEach(function(pair, index) {
      if (start > 0) return
      if (pair.first != pair.second) {
        start = index
      }
    })
    return start
  }

  var zip = getZip(
    original.split(''),
    newText.split('')
  )
  var diffStart = findDiffPoint(zip)
  var reverseZip = getZip(
    original.split('').reverse(),
    newText.split('').reverse()
  )

  var diffEnd = newText.length - findDiffPoint(reverseZip)

  var added = newText.slice(diffStart,diffEnd)

  return {
    start: diffStart,
    end: diffEnd,
    added: added
  }
}


var original = "first para\n Second para"
var newText =  "first para\n <b> INSERT </b> Second para"

diff = findDiff(original,newText)
console.log(
  diff
)</script></body>
</html>

## jsbin.nayedi.js
function findDiff(original, newText) {

  function getZip(originalList, newTextList){
    return originalList.map(function(char,i) {
      return {
        first: char,
        second: newTextList[i]
      }
    })
  }

  function findDiffPoint(zippedList) {
    var start = 0
    zippedList.forEach(function(pair, index) {
      if (start > 0) return
      if (pair.first != pair.second) {
        start = index
      }
    })
    return start
  }

  var zip = getZip(
    original.split(''),
    newText.split('')
  )
  var diffStart = findDiffPoint(zip)
  var reverseZip = getZip(
    original.split('').reverse(),
    newText.split('').reverse()
  )

  var diffEnd = newText.length - findDiffPoint(reverseZip)

  var added = newText.slice(diffStart,diffEnd)

  return {
    start: diffStart,
    end: diffEnd,
    added: added
  }
}


var original = "first para\n Second para"
var newText =  "first para\n <b> INSERT </b> Second para"

diff = findDiff(original,newText)
console.log(
  diff
)
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width">
	<title>JS Bin</title>
	</head>
	<body>

	<script id="jsbin-javascript">
	function findDiff(original, newText) {

	function getZip(originalList, newTextList){
	return originalList.map(function(char,i) {
	return {
	first: char,
	second: newTextList[i]
	}
	})
	}

	function findDiffPoint(zippedList) {
	var start = 0
	zippedList.forEach(function(pair, index) {
	if (start > 0) return
	if (pair.first != pair.second) {
	start = index
	}
	})
	return start
	}

	var zip = getZip(
	original.split(''),
	newText.split('')
	)
	var diffStart = findDiffPoint(zip)
	var reverseZip = getZip(
	original.split('').reverse(),
	newText.split('').reverse()
	)

	var diffEnd = newText.length - findDiffPoint(reverseZip)

	var added = newText.slice(diffStart,diffEnd)

	return {
	start: diffStart,
	end: diffEnd,
	added: added
	}
	}


	var original = "first para\n Second para"
	var newText = "first para\n <b> INSERT </b> Second para"

	diff = findDiff(original,newText)
	console.log(
	diff
	)
	</script>



	<script id="jsbin-source-javascript" type="text/javascript">function findDiff(original, newText) {

	function getZip(originalList, newTextList){
	return originalList.map(function(char,i) {
	return {
	first: char,
	second: newTextList[i]
	}
	})
	}

	function findDiffPoint(zippedList) {
	var start = 0
	zippedList.forEach(function(pair, index) {
	if (start > 0) return
	if (pair.first != pair.second) {
	start = index
	}
	})
	return start
	}

	var zip = getZip(
	original.split(''),
	newText.split('')
	)
	var diffStart = findDiffPoint(zip)
	var reverseZip = getZip(
	original.split('').reverse(),
	newText.split('').reverse()
	)

	var diffEnd = newText.length - findDiffPoint(reverseZip)

	var added = newText.slice(diffStart,diffEnd)

	return {
	start: diffStart,
	end: diffEnd,
	added: added
	}
	}


	var original = "first para\n Second para"
	var newText = "first para\n <b> INSERT </b> Second para"

	diff = findDiff(original,newText)
	console.log(
	diff
	)</script></body>
	</html>