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JavaScript

Navagating DOM Element properties in console.

So I enjoy the lessons but I'm trying to figure if I understand things or I'm just following along. I created my own variable

var paraOne = document.getElementsByTagName("p");

It returns p in the console. I want to select the first child but

paraOne.firstElementChild;

returns undefined. It should be the label element. Can you help explain what I'm donig wrong?

// Problem: User interaction doesn't provide desired results.
// Solution: Add interactivity so the user can manage daily tasks.

let taskInput = document.getElementById('new-task');//new-task
let addButton = document.getElementsByTagName('button')[0]; //first button
let incompleteTaskHolder = document.getElementById('incomplete-tasks');
let completedTaskHolder = document.getElementById('completed-tasks');
let paraOne = document.getElementsByTagName("p");

//Add a new task


let createNewTaskElement = function(){

let newTask = document.createElement("li");  
let checkBox = document.createElement("input");
let label = document.createElement("label");
let inputText = document.createElement("input");
let editButton = document.createElement("button");
let deleteButton = document.createElement("button");



  //When the button is pressed
  //Create a new list item with the text from #new-task:

  label.innerText = taskstring;

  newTask.appendChild(checkBox);
  newTask.appendChild(label);
  newTask.appendChild(inputText);
  newTask.appendChild(editButton);
  newTask.appendChild(deleteButton);




  return newTask;

  }

  let reLabel = function (){  
    let bob = paraOne.querySelector("input[type=text]");
    let paraVal = paraOne.getAttribute("");



    return reLabel;
  }  

let addTask = function() {
  let moreTask = createNewTaskElement("some new string");
  incompleteTaskHolder.appendChild(moreTask);
  bindTaskEvents(moreTask, taskCompleted);
  //input (Checkbox)

    //label
    //input (texts)
    //button.edit
    //button.delete
    //Each elements, need modified and appended

}

 //Edit an existing task
let editTask = function() {
    //When the Edit button is pressed
      //if the class of the parent is .editMode
        //Switch from .editMode
        //label texst become the input's value

}

  //Delete an existing task
    let deleteTask = function() {
      console.log("box is checked");
       //When the Delete button is pressed
          //Remove the parent list item from the url

    }


   let taskIncomplete = function() {
   console.log("Task incomplete..");
     let newTask = this.parentNode;
      incompleteTaskHolder.appendChild(newTask);
     bindTaskEvents(newTask,taskCompleted);
}



 //Mark a task as complete
    let taskCompleted = function() {
     //When the checkbox is unchecked
      //Append the task list item to the #incomplete-task
      let newTask = this.parentNode
      completedTaskHolder.appendChild(newTask);
       bindTaskEvents(newTask,taskIncomplete);
    }

let bindTaskEvents = function(taskListItem, checkBoxEventHandler){
  console.log("bind list item events");
//Select taskListItem's children
    let checkBox = taskListItem.querySelector("input[type=checkbox]");
    let editButton = taskListItem.querySelector("button.edit");
    let deleteButton = taskListItem.querySelector("button.delete");
  //bind editTask to edit button
    editButton.onclick= editTask;
  //bind deleteTask to delete button
    deleteButton.onclick = deleteTask;
  //bind checkBoxEventHandler to checkbox
    checkBox.onchange = checkBoxEventHandler;

}
//Set the click handler to teh addTask funciton
addButton.onclick = addTask;

//Cycle over the incompleteTaskHolder ul list item
for(let i = 0; i < incompleteTaskHolder.children.length; i++) {

  bindTaskEvents(incompleteTaskHolder.children[i],taskCompleted);

}
    //bind events to the list items children (taskCompleted)

for(let i = 0; i < completedTaskHolder.children.length; i++) {
  bindTaskEvents(completedTaskHolder.children[i], taskIncomplete);

}

2 Answers

Steven Parker
Steven Parker
216,012 Points

The property firstElementChild applies to individual elements.

But getElementsByTagName returns an element collection. You can get a single element from a collection by indexing, if you know which item you need.

For example, if paraOne is intended to be the first (index 0) paragraph, you could write this:

var paraOne = document.getElementsByTagName("p")[0];

Thank you, that was driving me crazy.