Introduction

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An AppJet app is a server-side JavaScript program that runs when a request is made to the app's domain (app-name.appjet.net).

Though AppJet is a server-side environment, the "core" JavaScript language is the same as you may be familiar with from the browser -- the same strings, objects, arrays, dates, and so on.

Beyond the core language is our set of libraries, which make it easy to build a simple web app.

Here is a complete AppJet app, a "shoutbox" where anyone can type in a message, and the most recent messages are displayed. It shows off persistent storage, responding to form input, and displaying HTML. Visit it at <http://shoutbox.jgate.de/>.

import("storage");
    
    var historySize = 20;
    
    if (! storage.msgs) {
        storage.msgs = new StorableObject();
        storage.start = 0; // first msg
        storage.end = 0; // index after last msg
    }
    
    if (request.isPost) {
        var newText = request.params.newText;
        if (acceptable(newText)) {
            storage.msgs[storage.end++] = request.params.newText;
            while (storage.end - storage.start > historySize) {
                delete storage.msgs[storage.start++];
            }
        }
        response.redirect("/");
    } else {
        print(FORM({id:"shoutform",action:"/", method:"post"},
              INPUT({type:"text", name:"newText", size:40}),
              INPUT({type:"submit", value:"shout!"})));
        var messageDiv = DIV({id:"msgs"});
        for(var i=storage.end-1; i >= storage.start; i--) {
            messageDiv.push(P(storage.msgs[i]));
        }
        print(messageDiv);
    }
    
    // TEMP: anti-spam tactics added to block annoying techcrunch spam.
    // We limit each IP address's posts.
    function acceptable(txt) {
        if (!storage.ips) { storage.ips = new StorableObject(); }
        if (!storage.ips[request.clientAddr]) {
            storage.ips[request.clientAddr] = 0;
        }
        storage.ips[request.clientAddr]++;
        return (storage.ips[request.clientAddr] <= 40 || 
                request.clientAddr == storage.ajtc);
    }
    
    /* appjet:css */
    
    #shoutform { margin: 10px; }
    #msgs { height: 200px; overflow: auto; border: 1px solid #666; 
      margin: 10px; padding-left: 10px; }
    #msgs p { margin-top: 0.6em; margin-bottom: 0.6em; }
    body { margin: 8px; padding: 0; margin-top: 6px; }