includes.html

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

/*
Prototype Function
 function includes(originalArray, searchValue, optionalStartingPostion) {
    var startingPosition = 0;
    if(arguments = 3) startingPosition = optionalStartingPostion; 
    for(var i = startingPosition; i < originalArray.length; i++) {
         if(originalArray[i] === searchValue)) {
             return true;
         }
     }
   return false;
 }
*/
   
function includes(originalArray, searchValue, optionalStartingPostion) {
    var startingPosition = 0;
    if(arguments.length === 3) {
        if(optionalStartingPostion < 0) {
          optionalStartingPostion = originalArray.length + optionalStartingPostion;
        }
        startingPosition = optionalStartingPostion; 
    }
    for(var i = startingPosition; i < originalArray.length; i++) {
         if(originalArray[i] === searchValue) {
             return true;
         }
     }
   return false;
 };



tests({

  'It should return a boolean': function() {
    var result = includes([1,2,3],3);
    eq(typeof result === 'boolean',true);
  },
  
  'It should return true if any element in the array matches the search value': function() {
    var result = includes([1,2,3],2);
    eq(result,true);
  },

  'It should return false if no element in array matches the search value': function() {
    var result = includes([1,2,3],4);
    eq(result,false);
  },

  'It should accept an optional starting position as third argument': function () {
    var result = includes([1,2,3,4],1,1);
    eq(result,false);
  },

  'If starting position is greater than the size of the array, false is returned': function () {
    var result = includes([1,2,3],1,3);
    eq(result,false);    
  },

  'If starting postion is negative, it is treated as an offset from the end of the array, e.g. -1 = last element in the array' : function () {
    var result = includes(['corn','wheat','rice'],'wheat',-1);
    eq(result,false);  
  }

});
</script>