Code structure

The first thing to study is the building blocks of the code.

Statements

Statements are syntax constructs and commands that perform actions.

We’ve already seen a statement alert('Hello, world!'), which shows the message.

We can have as many statements in the code as we want. Another statement can be separated with a semicolon.

For example, here we split the message into two:

alert('Hello'); alert('World');

Usually each statement is written on a separate line – thus the code becomes more readable:

alert('Hello');
alert('World');

Semicolons

A semicolon may be omitted in most cases when a line break exists.

This would also work:

alert('Hello')
alert('World')

Here JavaScript interprets the line break as an “implicit” semicolon. That’s also called an automatic semicolon insertion.

In most cases a newline implies a semicolon. But “in most cases” does not mean “always”!

There are cases when a newline does not mean a semicolon, for example:

alert(3 +
1
+ 2);

The code outputs 6, because JavaScript does not insert semicolons here. It is intuitively obvious that if the line ends with a plus "+", then it is an “incomplete expression”, no semicolon required. And in this case that works as intended.

But there are situations where JavaScript “fails” to assume a semicolon where it is really needed.

Errors which occur in such cases are quite hard to find and fix.

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About Mariano

I'm Ethan Mariano a software engineer by profession and reader/writter by passion.I have good understanding and knowledge of AngularJS, Database, javascript, web development, digital marketing and exploring other technologies related to Software development.