hello.md

Hop --- Hello World

The following example illustrates the Hop programming flavor:

★ Example: ls.hop.mjs

• The first three lines are regular JavaScript module imports. Note that Hop imposes to use ECMAScript modules on the server-side and client-side of the application.

• The variable hopConfig holds the server configuration used for that example. It will expect http connection on the port 8888 and it will allow unauthentified users to execute the service named ls;

• The variable hop is bound to the running Hop server and the variable R is bound to a static resolver of that service. It will be used to enable the server to delivery static page.

• The asynchronous function ls is the implementation of the unique service of this example. It takes an object as parameter that contains the name of the directory to be scaned. Using the Nodejs' asynchronous API it reads files on the disk and it builds the result as a web page. Inside an HTML fragments the syntax ${...} is similar to that of JavaScript string patterns. It insert the rsult of the evaluation in the HTML fragment that is finally assembled. Hop uses an extension to HTML to denote attributes that hold client side code. This is the ~{...} syntax. Inside a client code, the pattern ${...} is another sort of hole. It denotes a server side expression.

• The variable Ls is the Web service. The implementation is the function ls. As no URL is specified when the service is created, it takes its name from the JavaScript function. The URL for that service is then http://localhost:8888/ls.

• Finally, the last line of the program starts the web server.

Installation

A Hop program can be executed in a regular Node.js environment or in a native version. For the sake of simplicity we assume in this example an execution within Node.js.

To install the Hop dependencies to run this program, use the following package.json file:

{
   "name": "ls",
   "dependencies": {
     "@hop/hop": "file:/home/serrano/www/public_html/software/npmx/hop.tgz",
     "@hop/hopc": "file:/home/serrano/www/public_html/software/npmx/hopc.tgz"
   },
   "scripts": {
      "build": "./node_modules/@hop/hopc/bin/hopc.mjs ls.hop.mjs -o ls.mjs",
      "run": "node --enable-source-maps ls.mjs"
   }
}

and in the same directory

npm install
npm build

Finally, to run the program:

npm start

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