学習目的で、ローカルストレージで機能すると思われる簡単なメッセージングプログラムを作成しています。2次元配列に関するもう1つの質問は、コメントにあります。
<!DOCTYPE HTML> 
    <html>     
        <head>             
            <title>waGwan?</title>     
            <meta charset="utf-8"/>
            <link rel=stylesheet href=comm.css></link>       
        </head>     
            <body>                              
                <section>
                    <p>enter or create passcode: <input type=text id=passcode></p>
                    <input type=button id="button" value="send">
                </section>
                <section id="log"></section>
                <script type="text/javascript">
                    //initializing my passcode. Pass is a two dimensional array that holds passcodes and arrays of corresponding message logs; how can I instantiate my passcode without nil but maintain pass as a two dimensional array, just not include pass?
                    var pass=[mypasscode,nil];
                    document.getElementById("button").onclick=checkPass;
                    function checkPass(){
                        for(i=0;i<pass.length;i++){
                            //exits if passcode exists
                            if(document.getElementById("passcode").value==pass[i]){
                                break;
                            }
                            //if passcode doesn't equal last existing passcode the passcode and a new array (that stores the message log) is added to the pass array
                            else if(document.getElementById("passcode").value!==pass[pass.length-1]){
                                pass.push(document.getElementById("passcode").value,[We can chat here.]);
                            }
                        }
                        document.write("x");
                    }
                </script>
            </body> 
    </html>
    