Javascript has variables declared by using the let keyword. For example:

let a=1;  

Any time you declare a variable, you should have a semicolon at the end of the line.

Updating values in a variable

you can update a variable by using the equals sign:

let score=5;  
score=score+5;  

You can also use += to increment a value.

Old way of making variables

You can see in some old tutorials that they use var to declare variables instead of let. It still works but it is an outdated syntax.