bash.js

This piece of javascript code is an attempt to create a hybrid javascript and bash-like code runner. This runner was written to integrate with the mongoshell and provide more powerful command line query mechanisms.

The runner's goal is to have the advantages of the unix shell (pipes, commands, aliases...) combined with the ease of use of javascript.

Examples

Simple JavaScript

> 1 + 1
2

this example just show how normal javscript just runs as expected.

---

Commands

> id "xyz"
xyz

here we make use of the built-in id command that just returns the input parameter (here a simple string)

---

Pipes

> square 2 | _ + 2
4

it now gets interesting with the use of the pipe operator. the pipe operator will take the result of the left side and feed it to the right side under the _ variable.

note: here, the square command is a user-defined command

---

Mixed Pipes

> [1, 2, 3, 4] | Math.pow(2, _)
[2, 4, 8, 16]

when use with array, the pipe operator works as the javscript map function. the right side of the expression will then be called for every element of the array

---

Nested Expressions

> square (id 4 | Math.sqrt(_)) | repeat "!" _
!!!!

this example shows how it is possible to nest expressions and pipes while still mixing javascript and commands

Usage

Here is how you would use the runner:

var core = new Core();
core.run("1 + 1"); // => 2

The other nice thing about this project is how easy it is to add commands and aliases. Here's an example of adding the add command,

var core = new Core();
core.addCommand("add", function(x, y) {
	return x + y;
});

core.run("add 2 2"); // => 4

The last cool feature is also the support for aliases, for instance creating a increment alias for the add command,

core.addAlias("increment", "add 1 $1");

core.run("increment 1"); // => 2

Note: Accessing the alias' arguments is done using $n with n being the argument number, starting at 1.

Todo

• add support for iterator in pipeline to be able to integrate with the mongoshell's dbcursor, iterator can be created from:
  • an array
  • 2 functions: next and hasNext

License

bash.js is released under the MIT License.