Uncaught TypeError: Cannot read property 'querySelector' undefined

Könnten Sie mir helfen, bitte? Wenn ich diese ausführe, bekomme ich "Uncaught TypeError: Cannot read property 'querySelector' of undefined" in der "bindTaskEvents" - Funktion, wo die Funktion sich mit der "completedTasksHolder" - Liste. Versuchen Sie dies in der Konsole:

console.log(completedTasksHolder.children[0])

gibt die nur li Prima.

var taskInput = document.getElementById("new-task"); //new-task
var addButton = document.getElementsByTagName("button")[0]; //first button
var incompleteTasksHolder = document.getElementById("incomplete-tasks"); //ul#incomplete-tasks
var completedTasksHolder = document.getElementById("completed-tasks"); //ul#completed-tasks

//Add a new task
var addTask = function(){
    console.log("Add task...");
}
//Edit an existing task
var editTask = function() {
    console.log("Edit task...");
}

var deleteTask = function() {
    console.log("Delete task...");
//Delete an existing task

    //When the Delete button is pressed
        //Remove the parent li from the ul
}

var taskCompleted = function() {
    console.log("Complete task...");
//Mark a task as complete
    //When the checkbox is checked
        //Append the task li to the #completed-tasks
}

//Mark a task as incomplete
var taskIncomplete = function() {
    console.log("Incomplete task...");
    //When the checkbox is unchecked
        //Append the task li to the #incomplete-tasks
}

var bindTaskEvents = function(taskListItem, checkBoxEventHandler) {
    console.log("Bind li events");
    //select li's children
    var checkbox = taskListItem.querySelector("input[type=checkbox]");
    var editButton = taskListItem.querySelector("button.edit");
    var deleteButton = taskListItem.querySelector("button.delete");

    //bind editTask to editButton
    editButton.onclick = editTask;

    // bind deleteTask to deleteButton;
    deleteButton.onclick = deleteTask;

    //bind checkBoxEventHandler to checkbox
    checkbox.onchange = checkBoxEventHandler;
}

//Set the click handler to the addTask function
addButton.onclick = addTask;

//Cycle over incompleteTasksHiolder ul list items
for (var i = 0; incompleteTasksHolder.children.length; i++) {
        //bind events to li' children (taskCompleted)
    bindTaskEvents(incompleteTasksHolder.children[i], taskCompleted);
}     

//Cycle over completedTasksHiolder ul list items

for (var i = 0; completedTasksHolder.children.length; i++) {
        //bind events to li' children (taskCompleted)
    bindTaskEvents(completedTasksHolder.children[i], taskIncomplete);
}

Was kann hier falsch sein? Danke!

Was ist incompleteTasksHolder.children[i] ?
Es ist die ul (container) mit Liste posten wie die Kinder

InformationsquelleAutor Nikolay Komolov | 2016-04-06

javascript jquery

5

Problem mit der for-Schleife

Ersetzen
```
for (var i = 0; incompleteTasksHolder.children.length; i++) {
```
mit
```
for (var i = 0; i < incompleteTasksHolder.children.length; i++) {
```
ebenso für completedTasksHolder

Bascially, die Sie erstellt haben eine Schleife ohne Ende-Bedingung und irgendwann incompleteTasksHolder.children[i] ist undefined.
- Danke! Das ist die Lösung. Habt einen schönen Tag 🙂
- Willkommen, froh zu helfen 🙂
InformationsquelleAutor gurvinder372

JS:

var db = null;
var db2 = null;
var db3 = null;
var dbUser = null;
var dbName = "estudos.db";

var app = {
    //Application Constructor
    initialize: function() {
        document.addEventListener('deviceready', this.onDeviceReady.bind(this), false);
    },

    //deviceready Event Handler
    //
    //Bind any cordova events here. Common events are:
    //'pause', 'resume', etc.
    onDeviceReady: function() {
        this.receivedEvent('deviceready');
    },

    //Update DOM on a Received Event
    receivedEvent: function(id) {
        var parentElement = document.getElementById(id);
        var listeningElement = parentElement.querySelector('.listening');
        var receivedElement = parentElement.querySelector('.received');

        listeningElement.setAttribute('style', 'display:none;');
        receivedElement.setAttribute('style', 'display:block;');


        //OPERACOES BD - inicio

        //banco de dados local - aceite de termos e outras coisas
        dbUser = window.sqlitePlugin.openDatabase({name: 'user.db', location: 'default'});
        dbUser.transaction(function(tx) {
            tx.executeSql('CREATE TABLE IF NOT EXISTS Users (flg_aceite, flg_valid_bd)');
        }, function(error) {
            alert('Transaction ERROR: ' + error.message);
        }, function() {
            console.log('Database OK');
        });

        //copia do banco de dados de estudos
        window.plugins.sqlDB.copy(dbName, 0, copysuccess, copyerror);
        //OPERACOES BD - fim
    }
};

app.initialize();

//---------------------------------------------------------------

function copysuccess()
{
    //primeira versão deste banco de dados. o comando anterior.
    //provavelmente realizou a cópia, abro o BD.
    db = window.sqlitePlugin.openDatabase({name: dbName});
    //preciso verificar se existem versões anteriores deste BD. Deleto por precaucao
    dropTable();
    fts_table();
}

function copyerror(e)
{
    //esta versao do banco de dados ja existe.
    //abro o BD
    db = window.sqlitePlugin.openDatabase({name: dbName});
    //db3 = window.sqlitePlugin.openDatabase({name: "vtestudos"});
    //alert("copyerror" + JSON.stringify(e));
}


//---------------------------------------------------------------

function fts_table(){
    db.transaction(function(tx) {
    tx.executeSql('CREATE VIRTUAL TABLE vtestudos USING FTS3(titulo, texto, id_titulo)', [], function(tx,res){
          //alert("nao deu erro");
          //db = window.sqlitePlugin.openDatabase({name: "vtestudos"});
          //alert("uai. deu pra abrir");

          db.transaction(function(tx) {
          tx.executeSql('INSERT INTO vtestudos(titulo, texto, id_titulo) SELECT titulo, texto, id_titulo FROM estudos', [], function(tx,res){
              //db3 = window.sqlitePlugin.openDatabase({name: "vtestudos"});
               console.log('insert ok');
          });
          }, function(err){
              alert(err.message);
          });

    });
    }, function(err){
        alert(err.message);
    });
}

//---------------------------------------------------------------

function dropTable()
{
    window.plugins.sqlDB.remove("estudosprev1", 0, rmsuccess,rmerror); 
    window.plugins.sqlDB.remove("estudosprev2", 0, rmsuccess,rmerror);  
}

function rmsuccess()
{
    //existe versão anterior
    //alert("removesuccess");
    console.log('existe versão anterior');
}

function rmerror(e)
{
    //não existe versão anterior. ignoro.
    //alert("removeerror" + JSON.stringify(e));
    console.log('n existe versão anterior. ignoro.');
}

keine details, was es tut ?
Sie stellen die Funktionen für die Ausführung von code in der Datenbank.Aber wenn das ausgeführt in Android Studio. Zeigen Sie den Fehler-code:"Uncaught TypeError: Cannot read property 'querySelector" von null". Seine meine index.js Datei. Ich nicht Nein, wenn Sie bereits hatte es Problem bei der Ausführung mit phonegap/cordova in Android Studio. Dank

InformationsquelleAutor Gustavo Gonçalves

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