front-end-developer_1_
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Front-End-Developer - Level 1<br />
Try the confirm() function yourself, now.<br />
You should have seen that confirm() returns one of two values: true or false . Notice<br />
that there are no quotes around these values. true and false aren't strings - they're<br />
called booleans. They simply represent being true or false.<br />
And on that note, you might have noticed that alert() returned undefined , also without<br />
quotes. undefined simply represents that nothing has been returned from the function, or<br />
that a variable hasn't been assigned a value.<br />
Having now used numbers, strings, booleans, and undefined , you've come across four of<br />
the five basic JavaScript data types, or primitives. The last one is null , which represents<br />
nothingness. Don't worry about null for now - we'll learn more about it down the road.<br />
Summary<br />
A function is something that performs an action.<br />
A boolean is true or false .<br />
alert() opens a dialog box and returns undefined .<br />
confirm() opens a dialog box and returns a boolean.<br />
prompt() opens a dialog box and returns a string. The five JavaScript primitives are<br />
numbers, strings, booleans, undefined , and null .<br />
Everything after // is a comment and ignored by JavaScript.<br />
Functions<br />
113
Change language