1 00:00:00,210 --> 00:00:01,170 Welcome back. 2 00:00:01,170 --> 00:00:06,090 In this video we'll be talking about the fourth rule for determining what the key word this is and we'll 3 00:00:06,090 --> 00:00:10,810 recap all four rules to help you wrap your mind around this tricky topic. 4 00:00:10,830 --> 00:00:16,140 The fourth rule for determining the value of the keyword this is when you see the new keyword. 5 00:00:16,380 --> 00:00:19,870 The new keyword is a reserve keyword which does quite a few things. 6 00:00:20,010 --> 00:00:24,390 We'll be covering the New keyword in more depth in the object oriented programming section. 7 00:00:24,540 --> 00:00:30,660 But for now just know that when the new keyword is used a new object is created out of thin air. 8 00:00:30,660 --> 00:00:35,130 The new keyword is used with a function and inside of the function definition. 9 00:00:35,130 --> 00:00:39,140 The key word this refers to the new object that is created. 10 00:00:39,150 --> 00:00:45,060 Finally when the new keyword is used an implicit return this is added to the function which uses it 11 00:00:45,060 --> 00:00:46,020 . 12 00:00:46,020 --> 00:00:50,760 That sounds like a lot but will cover it in great detail and the object oriented programming section 13 00:00:50,760 --> 00:00:51,240 . 14 00:00:51,420 --> 00:00:54,060 For now let's take a look at this code example. 15 00:00:54,090 --> 00:00:57,310 We have a function called person which takes in two parameters. 16 00:00:57,390 --> 00:00:59,040 First name and last name. 17 00:00:59,370 --> 00:01:02,490 Inside of this function we're attaching properties on the keyword. 18 00:01:02,490 --> 00:01:05,950 This equal to the values passed to the function. 19 00:01:06,030 --> 00:01:08,970 You may be thinking hold on the value of the keyword. 20 00:01:08,970 --> 00:01:10,540 This is the global object. 21 00:01:10,620 --> 00:01:14,620 We saw that in a previous video and in fact you'd be absolutely right. 22 00:01:14,640 --> 00:01:19,090 However the value of the keyword this changes when we use the new keyword. 23 00:01:19,230 --> 00:01:25,260 Like we said before the keyword this now refers to an object that is created when the new keyword is 24 00:01:25,260 --> 00:01:26,180 used. 25 00:01:26,190 --> 00:01:31,500 We're storing that object in a variable called L-E and can then access the first name and last name 26 00:01:31,500 --> 00:01:33,340 properties on it. 27 00:01:33,360 --> 00:01:38,720 To recap we covered quite a lot in the section we examined the key word this which is a reserve key 28 00:01:38,720 --> 00:01:42,870 word in javascript and its value is determined at execution. 29 00:01:42,870 --> 00:01:47,970 We saw four rules global implicit explicit and the new keyword. 30 00:01:47,970 --> 00:01:53,550 When the keyword this is in the global context or in a function it is either the global object which 31 00:01:53,550 --> 00:01:54,210 is the window. 32 00:01:54,220 --> 00:02:00,300 If in the browser or undefined if we're using strict mode when the keyword this is inside of a declared 33 00:02:00,360 --> 00:02:05,940 object the value of the keyword this will always be the closest parent object. 34 00:02:05,940 --> 00:02:12,510 When we lose the context of the keyword this we can explicitly set the value using call apply or bind 35 00:02:12,530 --> 00:02:12,950 . 36 00:02:13,320 --> 00:02:16,800 Finally when the new key word is used the value of the keyword. 37 00:02:16,800 --> 00:02:23,210 This is set to an empty object and return from the function that is used with the new keyword. 38 00:02:23,220 --> 00:02:27,900 Congratulations you made it through the series on the keyword this pat yourself on the back. 39 00:02:27,900 --> 00:02:29,690 This is some complex material. 40 00:02:29,820 --> 00:02:34,050 If you're still tripped up try to walk through the code examples and be sure to ask us any questions 41 00:02:34,050 --> 00:02:34,140 . 42 00:02:34,140 --> 00:02:35,340 We're always happy to help. 43 00:02:35,490 --> 00:02:36,130 Thanks for watching