Javascript Code Contract Libraries?

I am just starting up a new web application and I want to implement some form of contract'esque style validation in my JavaScript. I did some quick googling, and came across JsCont

Solution 1:

Given that no one has recommended any existing libraries, or that I am crazy for thinking this is a good idea I went ahead and threw together a basic library. The code isn't fancy, but it does what I want, and it is reasonably fast to run (approx 40 chained checks per ms in IE).

I settled on a final syntax like:

function syncTime(serverTime, now) {
  Verify.value(serverTime).always().isDate();   // Cannot be undefined or null.
  Verify.value(now).whenDefined().isDate();     // Cannot be null, but must be date when defined.//Code
}

function searchForUser(firstName, middleInit, lastName) {
  Verify.value(firstName).always().isString().withMinimumLengthOf(2);  // Cannot be undefined or null.
  Verify.value(lastName).always().isString().withMinimumLengthOf(2);   // Cannot be undefined or null.
  Verify.value(middleInit).whenNotNull().isChar().between('A', 'Z');   // Cannot be undefined, but must be single char string when not null.//Code
}

I opted for an explicit 'Must Have Value' via the .always() check, personally I found it nicer to read; but I could see some going another way.

Given that the source is more than I want to post in this answer, please head to this CodePlex Wiki Page if you are interested in the source. I guess it turned in to more of a fluent assertion library; but it does what I need.

Update

I updated the source on the linked CodePlex page above. Specifically, I restructed the Verify class to make use of a 'value context' rather than always building new Verifier objects; improved IE's performance greatly (never was an issue with FireFox or Chrome)... now handles about 100 chained checks per ms in IE.

Solution 2:

I also have thrown together my idea of type contracts, which does what I want. A little late, I think, but I'll recommend it nevertheless for people willing to look at it: https://github.com/lindem/FirstContract

It's a WIP, but I needed something like it.

functionbmi (weight, height) {
    return weight / height * height;
}

var c = require("firstcontract").c
    /* 
     * contract applies to function taking two non-negative numbers,
     * returning a negative number: 
     */
    , contract = c(["R+0", "R+0"], "R+0")
    , cbmi = contract(bmi)
    ;

it was created so that I can add and remove it without changing the function monitored itself and provides just a clamp around the function. It's commonjs and on npm.

Solution 3:

One more - https://www.npmjs.com/package/bycontract It's a small library that expects JSDoc expressions (http://usejsdoc.org/) for a contract. A good chance for you are already familiar with the syntax.

Just see it in action:

// Simple testbyContract( true, "boolean" ); // ok// Multiple TypesbyContract( 100, "string|number|boolean" ); // ok // Optional Parametersfunctionfoo( bar, baz ) {
  byContract( arguments, [ "number=", "string=" ] );
}

Here kinda real-world example:

/**
 * @param {number|string} sum
 * @param {Object.<string, string>} payload
 * @param {function} cb
 * @returns {HTMLElement}
 */functionfoo( sum, payload, cb ) {
  // Test if the contract is respected at entry point byContract( arguments, [ "number|string", "Object.<string, string>", "function" ] );
  // .. var res = document.createElement( "div" );
  // Test if the contract is respected at exit point returnbyContract( res, HTMLElement );
}
// Test it foo( 100, { foo: "foo" }, function(){}); // ok foo( 100, { foo: 100 }, function(){}); // exception - ByContractError: Value of index 1 violates the contract `Object.<string, string>`