1 00:00:00,390 --> 00:00:03,690 Earlier you learned how to create or declare variables. 2 00:00:03,690 --> 00:00:07,470 For example, use the var keyword followed by a variable name. 3 00:00:07,470 --> 00:00:09,560 But you can't just use any word for 4 00:00:09,560 --> 00:00:12,150 a variable name, there are a few rules you should keep in mind. 5 00:00:13,360 --> 00:00:16,760 First, JavaScript has a long list of reserved words. 6 00:00:16,760 --> 00:00:19,330 These are words that are part of the JavaScript language itself, 7 00:00:19,330 --> 00:00:21,360 and are often called keywords. 8 00:00:21,360 --> 00:00:23,600 Var is an example of a reserved keyword. 9 00:00:23,600 --> 00:00:26,576 You can't create a variable named var, for instance. 10 00:00:26,576 --> 00:00:29,376 In the browser let's open up the console and 11 00:00:29,376 --> 00:00:33,096 see what happens if you try to create a variable named var. 12 00:00:38,340 --> 00:00:45,240 We get a syntax error, it says Uncaught SyntaxError Unexpected token var. 13 00:00:45,240 --> 00:00:49,190 A token is usually one of those reserved keywords I just talked about. 14 00:00:49,190 --> 00:00:52,820 This error usually means there's something in the code that shouldn't be there, 15 00:00:52,820 --> 00:00:54,820 like an unexpected character. 16 00:00:54,820 --> 00:00:57,280 And the JavaScript engine doesn't know what to do with it, like a typo. 17 00:00:57,280 --> 00:01:01,600 In this case, it's not able to create a variable name var, 18 00:01:01,600 --> 00:01:03,740 because var is a reserved word. 19 00:01:04,790 --> 00:01:08,700 JavaScript has a long list of reserved words which you will find in the lesson 20 00:01:08,700 --> 00:01:12,420 with this video, along with the other rules JavaScript has for naming variables. 21 00:01:12,420 --> 00:01:14,540 Now don't worry about memorizing the full list, 22 00:01:14,540 --> 00:01:17,100 you might even want to bookmark this page for future reference.