Trying JavaScript in the REPL

Trying JavaScript in the REPL

In this lesson, you opened Node’s REPL, tried a line of the setup check in it, and left it again.

• Run node with no arguments to open the REPL, the way python opens Python’s. Its prompt is > instead of >>>.
• Type a line, and the REPL echoes its value, as Python’s does. Strings come back in single quotes.
• The REPL echoes the value of every line. A console.log() line shows its output, then undefined, because console.log() returns undefined, JavaScript’s word for no value. Python’s print() returns None too, but Python’s REPL doesn’t echo None. A script never echoes, so the undefined never reaches the report.
• The up arrow brings back your last line. The REPL’s own commands start with a dot: .help lists them, and .exit leaves. Ctrl+D leaves too.
• node -p "expression" runs one expression from the shell and prints its value, where python -c prints only what you print().

Here’s the session from the video, after the banner:

> "request VPN access"
'request VPN access'
> console.log("1. request VPN access")
1. request VPN access
undefined