arity
v1.3.2
Published
Makes sure that JavaScript functions are called with the expected number and/or types of parameters.
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Arity
Makes sure that JavaScript functions are called with the expected number of parameters.
Background
Just like in any programming language JavaScript functions take parameters. Unlike many other programming languages, JavaScript does not require functions to be called with the defined number of parameters.
For example:
function sum(a, b) {
return a + b;
}
sum(1,2); // returns 3
sum(2); // returns NaN
Depending on the situation, it might be preferred that an error is thrown when the wrong number of parameters are passed in.
Usage
It's as simple as wrapping your function with ar
:
var sum = ar(function (a, b) {
return a + b;
});
sum(1,2); // returns 3
sum(2); // throws "Wrong number of parameters. Excpected 2, got 1. Params: a, b."
It's even easier in CoffeeScript (isn't everything?):
sum = ar (a, b) -> a + b
sum(1,2) // returns 3
sum(1,2,3) // throws "Wrong number of parameters. Excpected 2, got 3. Params: a, b."
Installing for Node.js
From the command-line:
npm install arity
From your app:
var ar = require("arity");
Installing for the browser
Download arity.js
and put it in your js
folder with your project. Then include it like so:
<script src="js/arity.js"></script>
You now have access to the ar
function.
Tests
npm install # Installs mocha
make test
Credit
Created by Jon Abrams.
Inspired by the rethinkDB's implementation.
I Found out about it from this blog post written by Andrew Berls.
License
Use it however you like, a warranty is neither implied nor provided.