CondJS

cond is hosted at Github. mona is a
public domain work, dedicated using
CC0 1.0. Feel free to do
whatever you want with it.

Quickstart

$3

$ npm install cond
or
$ bower install cond

$3

Execute the following in a browser session, with developer tools open, and
follow the instructions:

``javascript

var availableFlavors = ["chocolate", "vanilla", "mint chocolate chip"];
function getIceCream(flavor) {
if (availableFlavors.indexOf(flavor) !== -1) {
return flavor + " ice cream ゲットー!";
} else {
// Just like throw new Error("something"), but we provide a way
// the user can recover from it.
return cond.error("Sorry, that flavor is not available", [
"different-flavor", "Try a different flavor", getIceCream
], [
"add-flavor", "Add this flavor to available ones and retry", function() {
availableFlavors.push(flavor);
return getIceCream(flavor);
}
]);
}
}

console.log(getIceCream("coffee"));
console.log("I really like this flavor!");

// In the console, do:

// > showRecoveries();
// > recover(0, "chocolate");

// You can also access recoveries programmatically:
console.log(cond.handlerBind(function() {
return getIceCream("bubblegum");
}, [Error, function(e) { return cond.recover("add-flavor"); }]));
`

Introduction

cond` is a JavaScript implementation of
Common Lisp's condition system,
a system for handling errors and other conditions of interest that handles
signals at the call site, before the stack is unwound -- allowing you to repair
or alter what happens at the callsite, and continuing executing as if nothing
had been signaled/thrown.