Using of variables

In order to use a variable, you should first declare it: put the keyword let before its name. Let's declare, for example, the variable named a:

javascriptlet a;

After the variable declaration, you can write to it (they say to assign to it) some value, such as some number or string.

Writing data to a variable is done using the assignment operation =. Let's, for example, write the number 3 into the variable a:

javascriptlet a = 3;

And now let's display the contents of this variable on the screen using the alert function:

javascriptlet a = 3; // declaring a variable and assigning a value to it
alert(a);  // shows 3

It is not necessary to write the value into the variable immediately after the declaration. You can first declare a variable and then assign a value to it:

javascriptlet a;    // declaring a variable
a = 3;    // assigning value to it  
alert(a); // displays the value of the variable on the screen

As you see, let is written only once before a variable name - when you declare this variable. To use a variable further, you need only write the name of this variable.