fill.html

<script src="../simpleTest.js"></script>
<script>

// MDN Definition:
// The fill() method changes all elements in an array to a 
// static value, from a start index (default 0) to an 
// end index (default array.length). It returns the modified array.

// NOTES:

// fill REQUIREMENTS:

// DONE It should change elements in an array to a designated static value.
// DONE If start position is included as a thid argument, it should change array elements to static value from that index.
// DONE If end position is included as a fourth argument, it should stop changing elements in the array to static value once it reaches that index.
// DONE If no start is designated, it should begin with array[0].
// DONE If no end is designated, it should stop at array.length.
// DONE It should return the modified array.
// DONE It should modify the original array, not create a new array.
// DONE If start is negative, it should offset that many indexes from array.length.
// DONE If end is negative, it should offset that many indexes from array.length.
// DONE If start is greater than array.length, return array unmodified.
// DONE If calculated end is less than 0, return array unmodified.
// DONE If calculated start is less than 0, modify from beginning of the array until the end if designated, otherwise until array.length;

// DONE If the static value is an object, each modified spot should reference that same object.


function fill(array, staticValue, start, end) {
  var fixedStart = start;
  var fixedEnd = end;

  if (start) {
    if (start < 0) {
      if ((array.length + start) < 0) {
        fixedStart = 0;
      } else {
          fixedStart = array.length + start;
      }
    } else if (start > array.length) {
      return array;
    }
  }

  if (end) {
    if (end < 0) {
      if ((array.length + end) < 0) {
        return array;
      } else {
          fixedEnd = array.length + end;
      }
    } else if (end > array.length) {
        fixedEnd = array.length;
    }
  }



  if (arguments.length === 4) {
    for (var k = fixedStart; k < fixedEnd; k++) {
      array[k] = staticValue;
    }
  } else if (arguments.length === 3) {
    for (var j = fixedStart; j < array.length; j++) {
      array[j] = staticValue;
    }
  } else {
    for (var i = 0; i < array.length; i++) {
        array[i] = staticValue;
    }
  }
  return array;

}



tests({

  'It should change elements in an array to a designated static value.': function() {
    var myArray = ['old'];
    fill(myArray, 'new');
    eq(myArray, 'new');
  },
  'If start position is included as a third argument, it should change array elements to static value from that index.': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new', 1);
    eq(myArray[0], 'first');
    eq(myArray[1], 'new');
  },
  'If end position is included as a fourth argument, it should stop changing elements in the array to static value once it reaches that index.': function() {
    var myArray = ['first', 'second', 'third'];
    fill(myArray, 'new', 1, 2);
    eq(myArray[0], 'first');
    eq(myArray[1], 'new');
    eq(myArray[2], 'third');
  },
  'If no start is designated, it should begin with array[0].': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new');
    eq(myArray[0], 'new');
  },
  'If no end is designated, it should finish at array.length.': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new');
    eq(myArray[1], 'new');
  },
  'It should return the modified array': function() {
    var myArray = ['old'];
    var result = fill(myArray, 'new');
    eq(result, 'new');
    eq(result, myArray);
  },
  'It should modify the array, not create a new array.': function() {
    var myArray = ['old'];
    var result = fill(myArray, 'new');
    eq(result, myArray);
  },
  'If start is negative, it should offset that many indexes from array.length.': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new', -1);
    eq(myArray[0], 'first');
    eq(myArray[1], 'new');
  },
  'If end is negative, it should offset that many indexes from array.length.': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new', 0, -1);
    eq(myArray[0], 'new');
    eq(myArray[1], 'second');
  },
  'If start is greater than array.length, return array unmodified.': function() {
    var myArray = ['old'];
    var result = fill(myArray, 'new', 5);
    eq(result, 'old');
  },
  'If calculated end is less than 0, return array unmodified.': function() {
    var myArray = ['old'];
    var result = fill(myArray, 'new', 0, -5);
    eq(result, 'old');
  },
  'If calculated start is less than 0, modify from beginning of the array until the end if designated, otherwise until array.length;': function() {
    var myArray = ['first', 'second'];
    fill(myArray, 'new', -3, 1);
    eq(myArray[0], 'new');
    eq(myArray[1], 'second');
  },
  'If the static value is an object, each modified spot should reference that same object.': function() {
    var myArray = ['first', 'second'];
    var myElement = [[2]]
    fill(myArray, myElement);
    eq(myArray[0], myArray[1]);  
    myElement.push(3);
    eq(myArray[0].length, 2);
  }
  

});
</script>