opt-args v1.0.1

Simple and unobtrusive JS function overloads for optional arguments

Motivation

There are plenty of npm modules out there that let you do really complex, typed function overloading, but 90% of the time all that's needed is to create convenience methods with less parameters that 'drop' optional arguments.

For example, you might want a function with convenience overloads as follows:

var connect = function(host, port, timeout, handler) { }

connect('npmjs.com', 80, 30000, callback);

connect('npmjs.com', 80, callback);

connect('npmjs.com', callback);

connect('npmjs.com');

Implementing the above using the existing modules requires you to define multiple function bodies and add at least half a dozen lines of dead code.

I wanted to achieve this with concise syntax and minimal fuss based purely on the number of arguments passed in.

Approach

First let's deconstruct the overloading in the example above:

• 4 args: connect(host, port, timeout, callback)
• 3 args: connect(host, port, callback)
• 2 args: connect(host, callback)
• 1 args: connect(host)

You can see two clear groups of arguments here - those in italics are "dropped" before those in bold.

This can be represented by assigning a numerical priority to each parameter:

• host: 1
• port: 2
• timeout: 2
• callback: 1

Installation

npm install opt-args

Usage

opt-args allows you to assign a priority to each argument, controlling which arguments To achieve the overloading in the example above with opt-args, define your function as follows:

var opt = require('opt-args');

var connect = opt(1,2,2,1, function(host, port, timeout, handler) { });

That's it! Note that only a single funciton body is needed. opt-args ensures that values are routed to the correct parameters.

The four numbers (1,2,2,1) assign a priority to each of the four arguments, with lower values being of higher priority.

Lower priority arguments (higher numerical value) will be "dropped" first, and the right-most of two arguments with the same priority will be dropped first.

Any number of priority groups are supported.

License

ISC