"In a <code>constructor</code> the <code>this</code> variable refers to the new object being created by the constructor. So when we write,",
"<code> this.wheels = 4;</code>",
"inside of the <code>constructor</code> we are giving the new object it creates a property called <code>wheels</code> with a value of <code>4</code>.",
"You can think of a <code>constructor</code> as a description for the object it will create.",
"Have your <code>MotorBike</code> <code>constructor</code> describe an object with <code>wheels</code>, <code>engines</code> and <code>seats</code> properties and set them to numbers."
"assert(typeof (new MotorBike()).engines === 'number', 'message: <code>myMotorBike</code> should have a <code>engines</code> attribute set to a number.');",
"assert(typeof (new MotorBike()).wheels === 'number', 'message: <code>myMotorBike</code> should have a <code>wheels</code> attribute set to a number.');",
"assert(typeof (new MotorBike()).seats === 'number', 'message: <code>myMotorBike</code> should have a <code>seats</code> attribute set to a number.');"
"Note that it is important to use the <code>new</code> keyword when calling a constructor. This is how Javascript knows to create a new object and that all the references to <code>this</code> inside the constructor should be referring to this new object.",
"Now, once the <code>myCar</code> <code>instance</code> is created it can be used like any other object and can have its properties accessed and modified the same way you would usually. For example:",
"assert((new Car()).wheels === 4, 'message: The property <code>wheels</code> should still be <code>4</code> in the object <code>constructor</code>.');",
"assert(typeof (new Car()).nickname === 'undefined', 'message: There should not be a property <code>nickname</code> in the object <code>constructor</code>.');",
"assert(myCar.wheels === 4, 'message: The property <code>wheels</code> of <code>myCar</code> should equal <code>4</code>.');",
"assert(typeof myCar.nickname === 'string', 'message: The property <code>nickname</code> of <code>myCar</code> should be a string.');"
"Now we can pass in <code>arguments</code> when we call our <code>constructor</code>.",
"<code>var myCar = new Car(6, 3, 1);</code>",
"This code will create an object that uses the <code>arguments</code> we passed in and looks like:",
"<code>{</code>",
"<code> wheels: 6,</code>",
"<code> seats: 3,</code>",
"<code> engines: 1</code>",
"<code>}</code>",
"Now give it a try yourself! Alter the <code>Car</code> <code>constructor</code> to use <code>parameters</code> to assign values to the <code>wheels</code>, <code>seats</code>, and <code>engines</code> properties.",
"Then call your new <code>constructor</code> with three number <code>arguments</code> and assign it to <code>myCar</code> to see it in action."
"assert((function(){var testCar = new Car(3,1,2); return testCar.wheels === 3 && testCar.seats === 1 && testCar.engines === 2;})(), 'message: Calling <code>new Car(3,1,2)</code> should produce an object with a <code>wheels</code> property of <code>3</code>, a <code>seats</code> property of <code>1</code>, and an <code>engines</code> property of <code>2</code>.');",
"assert(typeof myCar.wheels === 'number' && typeof myCar.seats === 'number' && typeof myCar.engines === 'number', 'message: <code>myCar</code> should have number values for the <code>wheels</code>, <code>seats</code>, and <code>engines</code> properties.');"
"In the previous challenges, we used the <code>this</code> keyword to reference <code>public properties</code> of the current object.",
"We can also create <code>private properties</code> and <code>private methods</code>, which aren't accessible from outside the object.",
"To do this, we create the variable inside the <code>constructor</code> using the <code>var</code> keyword we're familiar with, instead of creating it as a <code>property</code> of <code>this</code>.",
"This is useful for when we need to store information about an object but we want to control how it is used by outside code.",
"For example, what if we want to store the <code>speed</code> our car is traveling at but we only want outside code to be able to modify it by accelerating or decelerating, so the speed changes in a controlled way?",
"In the editor you can see an example of a <code>Car</code> <code>constructor</code> that implements this pattern.",
"Now try it yourself! Modify the <code>Bike</code> <code>constructor</code> to have a <code>private property</code> called <code>gear</code> and two <code>public methods</code> called <code>getGear</code> and <code>setGear</code> to get and set that value."
"assert(typeof myBike.getGear !== 'undefined' && typeof(myBike.getGear) === 'function', 'message: The method <code>getGear</code> of <code>myBike</code> should be accessible outside the object.');",
"assert(typeof myBike.setGear !== 'undefined' && typeof(myBike.setGear) === 'function', 'message: The method <code>setGear</code> of <code>myBike</code> should be accessible outside the object.');",
"assert(typeof myBike.gear === 'undefined', 'message: <code>myBike.gear</code> should remain undefined.');"
"The <code>map</code> method will iterate through every element of the array, creating a new array with values that have been modified by the callback function, and return it.",
"In our example the callback only uses the value of the array element (the <code>val</code> argument) but your callback can also include arguments for the <code>index</code> and <code>array</code> being acted on.",
"The array method <code>reduce</code> is used to iterate through an array and condense it into one value.",
"To use <code>reduce</code> you pass in a callback whose arguments are an accumulator (in this case, <code>previousVal</code>) and the current value (<code>currentVal</code>).",
"<code>reduce</code> has an optional second argument which can be used to set the initial value of the accumulator. If no initial value is specified it will be the first array element and <code>currentVal</code> will start with the second array element.",
"assert(editor.getValue().match(/array\\.filter\\s*\\(/gi), 'message: You should be using the <code>filter</code> method to remove the values from the array.');",
"assert(editor.getValue().match(/\\[1\\,2\\,3\\,4\\,5\\,6\\,7\\,8\\,9\\,10\\]/gi), 'message: You should only be using <code>filter</code> to modify the contents of the array.');"
"You can use the method <code>sort</code> to easily sort the values in an array alphabetically or numerically.",
"Unlike the previous array methods we have been looking at, <code>sort</code> actually alters the array in place. However, it also returns this sorted array.",
"<code>sort</code> can be passed a compare function as a callback. If no compare function is passed in it will convert the values to strings and sort alphabetically.",
"Here is an example of using sort with a compare function that will sort the elements from smallest to largest number:",
"assert(editor.getValue().match(/\\[1\\,2\\,3\\,4\\,5\\,6\\,7/gi), 'message: You should only be using <code>reverse</code> to modify <code>array</code>.');"
"assert(editor.getValue().match(/\\.concat\\s*\\(/gi), 'message: You should be using the <code>concat</code> method to merge the two arrays.');",
"assert(editor.getValue().match(/\\[1\\,2\\,3\\]/gi) && editor.getValue().match(/\\[4\\,5\\,6\\]/gi), 'message: You should only be using <code>concat</code> to modify the arrays.');"
"The following is an example of using <code>join</code> to join all of the elements of an array into a string with all the elements separated by word `Na`:",
"Use the <code>join</code> method to create a string from <code>joinMe</code> with spaces in between each element and assign it to <code>joinedString</code>."
"assert(typeof(joinedString) === 'string' && joinedString === \"Split me into an array\", 'message: You should join the elements of the array with spaces.');",
"assert(/\\.join\\(/gi, 'message: You should use of the <code>join</code> method on the array.');"
