Annotate.js NPM

annotate.js - Asserts your function invariants

annotate.js allows you to attach certain metadata to your functions. For instance you could document invariants of your function this way. In addition you can attach an optional description you can access later on.

This metadata can be used by tools such as suite.js in order to generate tests. In addition you can access the metadata via REPL.

The usage is quite simple as the following example illustrates:

// let's define some function to annotate
function add(a, b) {
    return a + b;
}

// type checkers from is-js (https://npmjs.org/package/is-js)
var addNumbers = annotate(add, is.number, is.number, "Adds numbers");
var addStrings = annotate(add, is.string, is.string, "Adds strings");

// you can assert invariants too
var addPositiveNumbers = annotate(add, isPositive, isPositive, "Adds positive");

function isPositive(a) {
    return a >= 0;
}

The annotate function will create a new function that contains the metadata as properties \_doc and \_invariants. In case an invariant does not pass during execution, it won't execute. You will also receive a warning showing the status of invariants.