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Modules are formatted according to the CommonJS Module standard. This standard specifies that a module may be contained within a single JavaScript file with name module-name.js or in a directory named module-name containing a package.json file, which gives an object that defines properties of the module.

In addition, modules follow the Node Package Manager (npm) package name specification where package names are lower case and hyphenated. Host-specific modules should be in the @accessors-modules npm scope. An example of the correct way for an accessor to require a host-specific module is:

 var module = require('@accessors-modules/web-socket-client');

The host-specific implementation of require may remap the scope and package name.

For example, the Node Host module definitions in the @accessors-modules scope, which can be found at accessors/web/hosts/node/node_modules/@accessors-modules.

The JavaScript file or files in a module may define top-level variables, but these will be local to the module and not visible to the accessor script. A module makes its components available to the accessor script by defining fields of its exports field. For example, if the @accessors-modules/module-name/module-name.js file contains this:

   exports.moduleFunction = function() {...};

then the accessor script that requires a module that is not one of the Built-In JavaScript Modules can invoke the module's function as follows:

   var module = require('@accessors-modules/module-name');

Alternatively, the module JavaScript file can explicitly define the exports object as follows:

   var myFunction = function() {...};
   module.exports = {
       myFunction : myFunction

The require('@accessors-modules/module-name') call indicates to the accessor host that must have a locally installed implementation of the module in order to support this accessor. The host should reject the accessor if it does not have such an implementation installed.

Some hosts, such as the Node Host can install packages at run time using a package manager such as NPM. See accessors/web/hosts/node/node_modules/@accessors-modules/serial/serial.js. See Require Notes -> npm.

  • Require: require() can have a paths attribute

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Page last modified on June 08, 2017, at 03:00 am