d

Dynamic scope (emulation) in JavaScript

What

Chances are, you never heard of dynamic scoping.

But it is similar to other familliar concepts:

• *nix environment variables (ones you get from process.env)
• JavaScript's this (barely, but still)
• Global constants, except you can override them at call site

Usage

const d = require('@futpib/d');

function log(s) {
    const { output } = d.scope;
    output.write(s);
}

d.const({ output: process.stdin }, () => {
    log('hello');
    // Writes "hello" to standard input
});

d.const({ output: process.stderr }, () => {
    log('world');
    // Writes "world" to standard error
});

const fs = require('fs');

const logToFile = d.bind({ output: fs.createWriteStream('log.txt') }, log);

logToFile('fluff');
// Writes "fluff" to 'log.txt' in current directory

Install

yarn add @futpib/d

or

npm install @futpib/d

Performance

Keeping d.const and d.bind-created function calls outside tight loops seems like a good idea.

Check out index.benchmark.js.

Run via yarn benchmark.

Inspirations

• Common Lisp's defparameter and defvar