javascript - Web 浏览器中的 SQL 数据库存储 Javascript/HTML5

Question

在运行时创建的 SQLite 数据库中执行查询后显示结果时遇到问题。

这是我的代码

创建数据库

var mydb=false;

// initialise the database
initDB = function() {
  try { 
    if (!window.openDatabase) { 
      alert('not supported'); 
    } else { 
      var shortName = 'APP_DB'; 
      var version = '0.1'; 
      var displayName = 'It Happened Today DB'; 
      var maxSize = 262144; // in bytes, 256kb 
      mydb = openDatabase(shortName, version, displayName, maxSize); 
     }
  } catch(e) { 
    // Error handling code goes here. 
    if (e == INVALID_STATE_ERR) { 
      // Version number mismatch. 
      alert("Invalid database version."); 
    } else { 
      alert("Unknown error "+e+"."); 
    } 
    return; 
  } 
}

 // db error handler - prevents the rest of the transaction going ahead on failure
errorHandler = function (transaction, error) { 
  // returns true to rollback the transaction
  return true;  
} 

// null db data handler
nullDataHandler = function (transaction, results) { } 

创建表并插入值

 // create tables for the database
createTables = function() {

  try {
   mydb.transaction(
      function(transaction) {
        transaction.executeSql('CREATE TABLE milestones (ID INT( 10 ) NOT NULL, Title    VARCHAR( 50 )    DEFAULT NULL, mYear    INT( 11 )        NOT NULL, mMonth   INT( 11 )        DEFAULT NULL,  mDay     VARCHAR( 10 )    DEFAULT NULL, mText    VARCHAR( 2000 )  NOT NULL,  Theme1   VARCHAR( 50 )    DEFAULT NULL, Theme2   VARCHAR( 50 )    DEFAULT NULL, ImageURL VARCHAR( 50 )    DEFAULT NULL, PRIMARY KEY ( ID ));', [], nullDataHandler, errorHandler); 
        transaction.executeSql('INSERT INTO [milestones] ([ID], [Title], [mYear], [mMonth], [mDay], [mText], [Theme1], [Theme2], [ImageURL]) VALUES (2, "Cotton Mather", 1721, 6, 26, "Following the recommendation of Rev. Cotton Mather, Dr. Zabdiel Boylston of Boston completes the first inoculation against smallpox in the U.S., injecting his own son and two of his slaves.", "HIAm", null, "6-26 Cotton Mather3g04597v.jpg");', [], nullDataHandler, errorHandler); 
        transaction.executeSql('INSERT INTO [milestones] ([ID], [Title], [mYear], [mMonth], [mDay], [mText], [Theme1], [Theme2], [ImageURL]) VALUES (6, "New York Hospital", 1771, 6, 13, "New York Hospital, the second in the colonies after the Pennsylvania Hospital, receives a royal charter from King George III under the name Society of the Hospital in the City of New York in America, later changed to Society of New York Hospital.", "HIAm", null, "Default.png");', [], nullDataHandler, errorHandler); 
        });

  } catch(e) {
    /// alert(e.message);
    return;
  }
};

TEXT2HTML

milestonesDataHandler = function(transaction, results){
    var html = "";
    for(var i=0; i < results.rows.length; i++){
        var row = results.rows.item(i);
        html += '<li class="elist"> \
        <a href="article.template.html?id=">'+row['id']+'data-transition="none"> \
            <img src="img/">'+row['ImageURL']+'" height="70" width="70" /> \
            <h4>'+row['Title']+'</h4> \
            <p>'+ dateFormat($row['mYear']+' '+$row['mMonth']+' '+$row['mDay'])+'</p> \
        </a> \
        </li>';
    }
}

执行查询

loadMilestones = function(){
try {
    mydb.transaction(
        function(transaction){
            transaction.executeSql("SELECT * FROM milestones", [], milestonesDataHandler, errorHandler);
         });
}
 catch(e) {
    alert(e.message);
  }

}

在 HTML 文档的末尾，我这样做:

<script>$("div.miles").html(milestonesDataHandler);</script>

没有任何内容显示。当我进入 Chrome 调试器时，它显示:131 Uncaught TypeError:无法读取未定义的属性“长度”。

这是指 TEXT2HTML 部分的第三行。看起来由于某种原因，结果变量没有被填充。

您能帮我解决这个问题吗？

谢谢

Answer 1

createTables 未被调用，因此在调用 milestonesDataHandler 之前，未创建表或填充任何要显示的结果。