b70fed48a7
Fix #1484 Fix #1834 Fix #1482 Fix #771 It's been a while now, and we've seen how this separate context thing works. It constantly confuses people, and no one actually uses '.clear' anyway, so the benefit of that feature does not justify the constant WTFery. This makes repl.context actually be a getter that returns the global object, and prints a deprecation warning. The '.clear' command is gone, and will report that it's an invalid repl keyword. Tests updated to allow the require, module, and exports globals, which are still available in the repl just like they were before, by making them global.
3.2 KiB
REPL
A Read-Eval-Print-Loop (REPL) is available both as a standalone program and easily includable in other programs. REPL provides a way to interactively run JavaScript and see the results. It can be used for debugging, testing, or just trying things out.
By executing node without any arguments from the command-line you will be
dropped into the REPL. It has simplistic emacs line-editing.
mjr:~$ node
Type '.help' for options.
> a = [ 1, 2, 3];
[ 1, 2, 3 ]
> a.forEach(function (v) {
... console.log(v);
... });
1
2
3
For advanced line-editors, start node with the environmental variable NODE_NO_READLINE=1.
This will start the REPL in canonical terminal settings which will allow you to use with rlwrap.
For example, you could add this to your bashrc file:
alias node="env NODE_NO_READLINE=1 rlwrap node"
repl.start(prompt='> ', stream=process.stdin, eval=eval)
Starts a REPL with prompt as the prompt and stream for all I/O. prompt
is optional and defaults to > . stream is optional and defaults to
process.stdin. eval is optional too and defaults to async wrapper for eval.
You can use your own eval function if it has following signature:
function eval(cmd, callback) {
callback(null, result);
}
Multiple REPLs may be started against the same running instance of node. Each will share the same global object but will have unique I/O.
Here is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:
var net = require("net"),
repl = require("repl");
connections = 0;
repl.start("node via stdin> ");
net.createServer(function (socket) {
connections += 1;
repl.start("node via Unix socket> ", socket);
}).listen("/tmp/node-repl-sock");
net.createServer(function (socket) {
connections += 1;
repl.start("node via TCP socket> ", socket);
}).listen(5001);
Running this program from the command line will start a REPL on stdin. Other
REPL clients may connect through the Unix socket or TCP socket. telnet is useful
for connecting to TCP sockets, and socat can be used to connect to both Unix and
TCP sockets.
By starting a REPL from a Unix socket-based server instead of stdin, you can connect to a long-running node process without restarting it.
REPL Features
Inside the REPL, Control+D will exit. Multi-line expressions can be input.
The special variable _ (underscore) contains the result of the last expression.
> [ "a", "b", "c" ]
[ 'a', 'b', 'c' ]
> _.length
3
> _ += 1
4
The REPL provides access to any variables in the global scope.
There are a few special REPL commands:
.break- While inputting a multi-line expression, sometimes you get lost or just don't care about completing it..breakwill start over..exit- Close the I/O stream, which will cause the REPL to exit..help- Show this list of special commands.
The following key combinations in the REPL have these special effects:
<ctrl>C- Similar to the.breakkeyword. Terminates the current command. Press twice on a blank line to forcibly exit.<ctrl>D- Similar to the.exitkeyword.