Sequencing

By calling one function after another, in sequence, you can have the program do different things in sequence.

doSomething();
doAnotherThing();

The semicolon

In JavaScript, the semicolon (;) is used to terminate (or end) a statement. However, in most cases, the semicolon is optional and can be omitted. So both code sequences below are legal:

doSomething()
doAnotherThing()

doSomething();
doAnotherThing();

The empty statement

In JavaScript, there is the concept of an empty statement, which is whitespace followed by a semicolon in the context where a statement is expected. So, the following code is an infinite loop followed by a call to doSomething that will never execute:

while(true) ;
doSomething(); // THIS LINE WILL NEVER EXECUTE!

while(true) { } 
doSomething(); // THIS LINE WILL NEVER EXECUTE!

Read more about semicolons in JavaScript.