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Now that I had a quick look at the very basics and the core terms you have to know, let's dive into some

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next gen javascript syntax you'll see throughout this module or throughout this course. Var is a keyword that

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creates a new variable

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and actually it's a bit of an outdated syntax, from now on we'll use let instead of var and let also

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creates a variable, the scoping behaves a bit differently but we can ignore that for now

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here, check out some next-gen javascript resource like my ES6 course or of course also some free resources

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to learn all about let

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but the core reason for using let is that we now also have another way of creating a variable and with

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that, I mean a variable which never changes which actually is the case for all three here.

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But let's say we actually do assign a new value to age here but we never change name or has hobbies,

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we could absolutely use let,

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there is nothing strictly wrong with that

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but to be clear about our intentions in the code and we know that we'll never change

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let name and has hobbies,

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we can also use a new keyword available in javascript and that's the const keyword. This creates a

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so-called constant

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and this makes clear that we never plan on changing the value of name or has hobbies.

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We do plan to change it of age

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and that is why we have let and that is the reason why we have two different keywords for creating variables,

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though

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again these are not really variables, they are constants, either const or let depending on whether you

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plan to change this or not.

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So now if I execute this, it works in exactly the same way as before but by the way, if I would try to set name

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to Maximillian here and I do run node play.js again, I actually get an error

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now, that I try to assign to a constant variable. So this actually already shows us the idea behind const

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and you want to use const as often as possible to be as clear about what happens in your code as possible

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and if something should never change, make it a const so that you get an error

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if you do accidentally change it. So here I'll revert this change

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but I wanted to show you how let and const work.