iot-backend/software/flow/node_modules/install/README.md

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2023-02-23 15:38:30 +01:00
# install [![Build Status](https://travis-ci.org/benjamn/install.svg?branch=master)](https://travis-ci.org/benjamn/install) [![Greenkeeper badge](https://badges.greenkeeper.io/benjamn/install.svg)](https://greenkeeper.io/)
The [CommonJS module syntax](http://wiki.commonjs.org/wiki/Modules/1.1) is one of the most widely accepted conventions in the JavaScript ecosystem. Everyone seems to agree that `require` and `exports` are a reasonable way of expressing module dependencies and interfaces, and the tools for managing modular code are getting better all the time.
Much less of a consensus has developed around the best way to deliver CommonJS modules to a web browser, where the synchronous semantics of `require` pose a non-trivial implementation challenge. This module loader contributes to that confusion, yet also demonstrates that an amply-featured module loader need not stretch into the hundreds or thousands of lines.
Installation
---
From NPM:
npm install install
From GitHub:
cd path/to/node_modules
git clone git://github.com/benjamn/install.git
cd install
npm install .
Usage
---
The first step is to create an `install` function by calling the
`makeInstaller` method. Note that all of the options described below are
optional:
```js
var install = require("install").makeInstaller({
// Optional list of file extensions to be appended to required module
// identifiers if they do not exactly match an installed module.
extensions: [".js", ".json"],
// If defined, the options.fallback function will be called when no
// installed module is found for a required module identifier. Often
// options.fallback will be implemented in terms of the native Node
// require function, which has the ability to load binary modules.
fallback,
// Boolean flag indicating whether the installed code will be running in
// a web browser.
browser,
// List of fields to look for in package.json files to determine the
// main entry module of the package. The first field listed here whose
// value is a string will be used to resolve the entry module. Defaults
// to just ["main"], or ["browser", "main"] if options.browser is true.
mainFields: ["browser", "main"],
});
```
The second step is to install some modules by passing a nested tree of
objects and functions to the `install` function:
```js
var require = install({
"main.js"(require, exports, module) {
// On the client, the "assert" module should be install-ed just like
// any other module. On the server, since "assert" is a built-in Node
// module, it may make sense to let the options.fallback function
// handle such requirements. Both ways work equally well.
var assert = require("assert");
assert.strictEqual(
// This require function uses the same lookup rules as Node, so it
// will find "package" in the "node_modules" directory below.
require("package").name,
"/node_modules/package/entry.js"
);
exports.name = module.id;
},
node_modules: {
package: {
// If package.json is not defined, a module called "index.js" will
// be used as the main entry point for the package. Otherwise the
// exports.main property will identify the entry point.
"package.json"(require, exports, module) {
exports.name = "package";
exports.version = "0.1.0";
exports.main = "entry.js";
},
"entry.js"(require, exports, module) {
exports.name = module.id;
}
}
}
});
```
Note that the `install` function merely installs modules without
evaluating them, so the third and final step is to `require` any entry
point modules that you wish to evaluate:
```js
console.log(require("./main").name);
// => "/main.js"
```
This is the "root" `require` function returned by the `install`
function. If you're using the `install` package in a CommonJS environment
like Node, be careful that you don't overwrite the `require` function
provided by that system.
If you need to change the behavior of the `module` object that each module
function receives as its third parameter, the shared `Module` constructor
is exposed as a property of the `install` function returned by the
`makeInstaller` factory:
```js
var install = makeInstaller(options);
var proto = install.Module.prototype;
// Wrap all Module.prototype.require calls with some sort of logging.
proto.require = wrapWithLogging(proto.require);
// Add a new method available to all modules via module.newMethod(...).
proto.newMethod = function () {...};
```
Many more examples of how to use the `install` package can be found in the
[tests](https://github.com/benjamn/install/blob/master/test/run.js).