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Var 1/3
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Var:
In the very first chapter of the section we learn that there are three ways to declare a variable:
letconstvar
The var is used as an alternative to the let keyword. We can replace let with the var or vice-versa but there are some exceptions.
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Declare a variable with the identifier name customers and assign the value 1000 by using the var keyword. Show the value on the console.
解答
Var has No Block Scope
Variables have either local-scope or global-scope. The code which is enclosed inside the {} is called a block of code. Variables declared with var are accessible outside the block as well, for example.
1234if (10 > 5){ var test = true; } console.log(test);
But if we declare the test variable with the let keyword we get an error.
1234if (10 > 5){ let test = true; } console.log(test);
As you can see that the test variable was accessible outside the if statement when declared with the var keyword, but it was not accessible when declared with the let keyword.
Note: Scoping is an advanced topic therefore this part has no exercise because we will learn more about the scope in the upcoming chapters.
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