find.html

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

// Prototype Function
//  function find(originalArray, callback) {
//      for(var i = 0; i < originalArray.length; i++) {
//          if(callback(originalArray[i], i, originalArray)) {
//              return array[i];
//          }
//      }
//  }

  

function myFind(originalArray,callback, optionalThisArgument) {
    var findCallback = callback;
    var maxRunCount = originalArray.length;
    if(arguments.length >= 3) {
        findCallback = callback.bind(optionalThisArgument);
    }
    for(var i = 0; i < maxRunCount; i++) {
         if(findCallback(originalArray[i], i, originalArray)) {
             return originalArray[i];
         }
     }
};

tests({

  'It should return the first element in the array that the callback returns true.': function() {
    var result = myFind([1,2,3],function(number){
        return number > 2;
    })  
    eq(result,3);
  },

  'It should return undefined if no element in array returns true by callback': function() {
    var result = myFind([1,2,3],function(number){
        return number > 3;
    })  
    eq(result,undefined);
  },

  'It should pass in the ith element as the first argument to the callback': function() {
    myFind([3],function(number){
      eq(3, number);
    })
  },

  'It should pass in the index as the second arguement to the callback': function() {
    myFind([1],function(number, index){
      eq(0,index);
    })
  },

  'It should pass in the original array as the third argument to the callback': function() {
    var testArray = [1,2,3];
    myFind(testArray, function (number, index, originalArray){
      eq(originalArray,testArray);
    })
  },

  'It should accept an optional this object': function () {
    myFind([1], function() {
      eq(this.description,"I should be accessible within the callback");
    }, {description:"I should be accessible within the callback"}) 
  },

  'It should not modify the original array': function () {
    var testArray = [1,2,3];
    var testCopy = [1,2,3];
    myFind(testArray,function (number,index, array){
        eq(array[index],testCopy[index]);
    });    
  },

  'It should run <= originalArray.length times.': function () {
    var runCount = 0;
    myFind([1,2,3],function(number, index, array){
      runCount++;
      array.push('66');
    })
    eq(runCount,3);
  }

});
</script>