为什么我总是从Chrome中获得“Uncaught SyntaxError：Unexpected token u”？

Question

我已经花了整整一天的时间，使用Google搜索并寻找答案，但仍然无法弄清楚。

我的代码有点长，它在Firefox中运行良好，但从Chrome获取“Uncaught SyntaxError：Unexpected token u”。

任何人都可以指出我哪里错了吗？提前致谢！

// when the page loads, list all the current contacts 
$(document).ready(function(){ 

    // check if localStorage database exists 
    if(!localStorage.getItem("customerDatabase")){ 

     // define a JSON object to hold all current address 
     var contacts = { 
      "users":[ 
       { 
        "id":"1", 
        "name":"dennis", 
        "email":"dennisboys@gmail.com" 
       }, 
       { 
        "id":"2", 
        "name":"zoe", 
        "email":"zoeisfemale@gmail.com"    
       } 
      ] 
     } // end of contacts JSON object 

     // stringify the object 
     var stringObject = JSON.stringify(contacts);     

     // store it into localStorage database 
     var storedDatabase = localStorage.setItem("customerDatabase", stringObject);            

    } else { 
     // list all customers upon page loads 
     listJSONCustomers();   
    } 

    // list all current contacts from JSON object in localStorage 
    function listJSONCustomers(){ 

     var displayHTML = ""; 
     var i; 

     // get the data from localStorage 
     var storedDatabase = localStorage.getItem("customerDatabase"); 

     // parse the data from string to JSON object 
     var parseObject = JSON.parse(storedDatabase); 

     // access the users key of the JSON object 
     var userObject = parseObject.users; 

     // get the length of the object (how many customers the database has) 
     var contactsLength = userObject.length;  

     for(i=0; i<contactsLength; i++){ 
      var trElement = '<tr id="address' + (i+1) + '">'; 
      var tdId = '<td id="id' + (i+1) + '">' + userObject[i].id + '</td>'; 
      var tdName = '<td id="name' + (i+1) + '">' + userObject[i].name + '</td>'; 
      var tdEmail = '<td id="email' + (i+1) + '">' + userObject[i].email + '</td>'; 
      var tdButton = '<td id="button"><button id="editButton' + userObject[i].id + '">Edit</button> | <button id="deleteButton' + userObject[i].id + '">Delete</button></td>'; 

      displayHTML += trElement + tdId + tdName + tdEmail + tdButton + '</tr>'; 
     }  

     $('#address_list').html(displayHTML);   
    }  

    // add customer to database 
    $('#saveCustomer').click(function(){ 

     if($('#customerName').val() !== "" && $('#customerEmail').val() !== ""){ 

      var customerName = $('#customerName').val(); 
      var customerEmail = $('#customerEmail').val(); 

      // get the data from localStorage 
      var storedDatabase = localStorage.getItem("customerDatabase"); 

      // parse the data from string to JSON object 
      var parseObject = JSON.parse(storedDatabase);  

      // access the users key of the JSON object 
      var userObject = parseObject.users;  

      // get the new entry 
      var newCustomerObject = { 
            "id": userObject.length + 1, 
            "name": customerName, 
            "email": customerEmail 
            }; 

      // push the new entry into the object                
      userObject.push(newCustomerObject); 

      // convert the object into string for localStorage 
      var stringObject = JSON.stringify(parseObject);   

      // store the JSON object into localStorage 
      var storedDatabase = localStorage.setItem("customerDatabase", stringObject); 

      // list all customes again every time a database receives a new entry 
      listJSONCustomers();  

     } else { 
      alert("Please enter customer's name and email."); 
     } 

    }); // end of $('#saveCustomer').click(); 


}); 

Answer 1

在某些情况下，您确实损坏了LocalStorage对该密钥的价值。 LocalStorage只能存储字符串，所以如果你传递任何东西给它，它会将它转换为一个字符串。因为你的价值是'undefined'，这意味着，在某些时候，你可能没有事故是这样的：

var value; 
localStorage.setItem('key', value); 

在这种情况下，value为undefined，这不是一个字符串。当它被保存时，它将被转换。不幸的是，"undefined"是无效的JSON。这意味着当它试图解析时，它会抛出异常。

要解决您的问题，您应该清除与removeItem出错的值。

localStorage.removeItem("customerDatabase");