pxt-calliope/docs/javascript/sequence.md

Sequencing

By calling one function after another, in sequence, you can create an animation:

basic.showLeds(`
    . # . # .
    . . . . .
    . . # . .
    # . . . #
    . # # # .
    `);
basic.showLeds(`
    . # . # .
    . . . . .
    . . . . .
    . # # # .
    # . . . #
    `);

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:

basic.showNumber(1)
basic.showNumber(2)

basic.showNumber(1); 
basic.showNumber(2);

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 showNumber that will never execute:

while(true) ;
basic.showNumber(1);

~hint

For the @boardname@, we don't allow a program to contain an empty statement, such as shown above. If you really want an empty statement, you need to use curly braces to delimit an empty statement block:

while(true) { } 
basic.showNumber(1);

~

Read more about semicolons in JavaScript.