Defining a Variable with let2:48 with Andrew Chalkley
Using constants is are a best practice when assigning variables but what happens when you do actually want to reassign a value? That's where let comes in.
The let keyword is used when you want to re-assign a variable. 0:00 In that respect, It just works like var. 0:04 Let's take a look at a simple example. 0:07 Open up let.html, and you can see we've got the score = 0 and 0:09 age = 33, and a boolean is hungry = false. 0:16 Open up the preview and navigate to let.html. 0:22 Open up the console, and let's try and modify the score. 0:28 The score can change through a game. 0:36 The score increments by one each time the player completes a challenge. 0:38 Again, let just works like var. 0:43 You can reassign values to a variable that is declared with the let keyword. 0:47 You can update the age to be 34. 0:53 And is hungry. 0:57 To be true. 1:05 Let's look at a more complex example where you should use let rather than a const. 1:07 Open up person.html, and here we have a function called 1:14 personDescription that creates a description string. 1:18 That gets logged out at the end here. 1:24 If the person object has a role, 1:27 it will add additional information at the end of the description and is logged out. 1:33 Let's see this in action. 1:40 Go to the preview. 1:42 Click on person.html, 1:43 open up the developer console and we should see Andrew is a teacher. 1:46 If we change the var keyword in the person description function to const. 1:52 And run it again we get an error, because we're trying to re-assign the description 1:59 in the if block, We could change it to var, 2:06 or alternatively we could use the new let keyword. 2:12 Let works like var, allowing you to re-assign variables, but 2:18 unlike var, it has block level scoping. 2:23 We'll explore when we'd see the advantages of using let over var in the next video. 2:26 Now that we've changed the const to let, let's see how it works in our browser. 2:32 Looking in the console, we see Andrew is a teacher printed out like we expect. 2:38 In the next video, 2:42 we'll look at how let solved some problems where the var keyword falls short. 2:43
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