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<!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 findLowIndex(arr, key) {
  var low = 0;
  var high = arr.length - 1;

  var mid = Math.floor(high /2);

  while(low <= high) {

    if(arr[mid] < key) {
      low = mid + 1;
    } else {
      high = mid - 1;
    }

    mid = low + Math.floor((high - low) / 2);
  }

  if(arr[low] === key) {
    return low;
  }

  return - 1;
}

console.log(findLowIndex([1,2,5,5,5,5,5,5,5,5,20], 5));


function findHighIndex(arr, key) {
  var low = 0;
  var high = arr.length - 1;
  var mid = Math.floor(high / 2);

  while(low <= high){

    if(arr[mid] < key){
      low = mid + 1;
    } else {
      high = mid - 1;
    }

    mid = low + Math.floor((high - low) / 2);
  }

  if(arr[high] === key){
    return high;
  }

  return -1;

}
</script>


<script id="jsbin-source-javascript" type="text/javascript">function findLowIndex(arr, key) {
  var low = 0;
  var high = arr.length - 1;

  var mid = Math.floor(high /2);

  while(low <= high) {

    if(arr[mid] < key) {
      low = mid + 1;
    } else {
      high = mid - 1;
    }

    mid = low + Math.floor((high - low) / 2);
  }

  if(arr[low] === key) {
    return low;
  }

  return - 1;
}

console.log(findLowIndex([1,2,5,5,5,5,5,5,5,5,20], 5));


function findHighIndex(arr, key) {
  var low = 0;
  var high = arr.length - 1;
  var mid = Math.floor(high / 2);

  while(low <= high){

    if(arr[mid] < key){
      low = mid + 1;
    } else {
      high = mid - 1;
    }

    mid = low + Math.floor((high - low) / 2);
  }

  if(arr[high] === key){
    return high;
  }

  return -1;

}
</script></body>
</html>