underscore_lab_pt_1.js

// PUT YOUR CODE HERE!!!
var _ = {
  average: function(array) {
  if (!Array.isArray(array)){ return "can only find average of numbers." }

    var length = array.length;
    var sum = 0;

    for (var i = 0; i < length; i += 1) {
      sum += array[i];
    }
    return sum / length;
  },
  contains: function(array, number) {
      var length = array.length;

      for (var i = 0; i < length; i += 1) {
        if (array[i] === number) {
          return true
        }
      }
      return false;
  },
  first: function(array) {
    return array[0];
  },
  last: function(array) {
    return array[array.length - 1]
  },
  max: function(array) {
    var length = array.length;
    var maximum = 0;

    for (var i = 0; i < length; i += 1) {
      if (array[i] > maximum) {
        maximum = array[i];
      }
    }
    return maximum;
  },
  min: function(array) {
    var length = array.length;
    var min;

    for (var i = 0; i < length; i += 1) {
      if (min === undefined || array[i] < min) {
        min = array[i]
      }
    }
    return min;
  },
  shuffle: function(array) {
    var newArr = [];
    var index = array.length;
    var tempVar;
    var randomIndex;

    for (var i = length; i > 0; i -= 1) {
      randomIndex = Math.floor(Math.random() * (i + 1));

      tempVar = array[randomIndex];
      array[randomIndex] = array[i];
      array[i] = tempVar;
    }
    return array;
  },
  sample: function(array, elements) {
    var randomElements = [];
    var random;
    var indexToRemove;

    if (!elements) { return array[Math.floor(Math.random() * (length - 1))] }

    for (var i = 1; i <= elements; i += 1) {
      random = Math.floor(Math.random() * (array.length - 1));
      randomElements.push(array[random])  ;
      indexToRemove = array.indexOf(array[random]);
      array.splice(indexToRemove, 1);
    }
    return randomElements;
  },





  difference: function(array1, array2) {
    var diffArray = [];

    for (var i = 0; i < array2.length; i += 1) {
      for (var j = 0; j < array1.length; j += 1) {
        if (!(array1[j] === array2[i]) && diffArray.indexOf(array1[i]) === -1) {
          diffArray.push(array1[i]);
        }
      }
    }
    return diffArray;
  },
  indexOf: function(array, value) {
    for (var i = 0; i < array.length; i += 1) {
      if (array[i] === value) {
        return i;
      }
    }
    return -1;
  },
  pluck: function(array, propName) {
    var propValues = [];

    for (var i = 0; i < array.length; i += 1) {
      propValues.push(array[i][propName]);
    }
    return propValues;
  }
}