Fundamentals 編

JSchallenger にチャレンジ - Fundamentals / Basics
JSchallenger にチャレンジ - Fundamentals / Arrays
JSchallenger にチャレンジ - Fundamentals / Objects
JSchallenger にチャレンジ - Fundamentals / Dates
JSchallenger にチャレンジ - Fundamentals / Sets

DOM 編

JSchallenger にチャレンジ - DOM / DOM selector methods
JSchallenger にチャレンジ - DOM / Events and user interactions
JSchallenger にチャレンジ - DOM / DOM manipulation
JSchallenger にチャレンジ - DOM / DOM fundamentals
JSchallenger にチャレンジ - DOM / Recursive functions

cyamy 2022/07/10に更新

Select the button element on the page

In this scenario, the existing code adds an eventListener for a click event on a variable 'buttonElem'. It expects 'buttonElem' to be the button element in the example UI. But, that element is not selected yet.
Assign the button element to the variable 'buttonElem' with one of the existing selector methods.
Click the button to verify that the code is working.
Hint: Make use of the unique id identifier of the button element.

回答

const buttonElem = document.getElementById('button')

buttonElem.addEventListener('click', () => {
  const oldText = buttonElem.innerText;
  return button.innerText = oldText === "ON" ? "OFF" : "ON";
});

cyamy 2022/07/10に更新

Query descendent HTML elements

Here, the existing code expects the variables 'buttonElem' and 'inputElem' to represent the button and input elements in the example UI.
Assign the respective elements to the variables.
In this case, the two elements do not have unique identifiers - like for example an id. Instead they are direct descendents of a div element with id 'wrapper'. Use an appropriate selector method!
Click the button to verify that the code is working.

回答

const buttonElem = document.querySelector('#wrapper > button')
const inputElem = document.querySelector('#wrapper > input')

buttonElem.addEventListener('click', () => {
  const oldText = inputElem.value;
  return inputElem.value = oldText === "ON" ? "OFF" : "ON";
});

cyamy 2022/07/10に更新

Select multiple HTML elements

In this scenario, we are looking for a list of elements gathered in one variable - rather than only one element.
Assign the list items in the view to the variable 'listItems' by using an appropriate selector method.
Once you have completed the code below, verify it by hovering over the list items until all items have the value 'ON'

回答

const listItems = document.querySelectorAll("#list > li");

const handleHover = (event) => {
  return event.target.innerText = 'ON';
};
if(listItems.length > 1) {
  listItems.forEach(item => item.addEventListener('mouseover', handleHover));
}

cyamy 2022/07/10に更新

Query and exclude HTML elements

In this scenario, you need to query all list items that belong to the list with id 'list'. But, exclude the ones with id 'disabled'
Assign those items to the variable 'listItems' by using an appropriate selector method.
Once you have completed the code below, verify it by clicking the button. The respective items should change their text.

回答

const targets = document.querySelectorAll("#list > li");
const listItems = Array.from(targets).filter(cur => cur.id !== 'disabled')

const button = document.getElementById('button');

const handleClick = () => {
  listItems.forEach(item => {
  const oldText = item.innerText;
    return item.innerText = oldText === 'ON' ? 'OFF' : 'ON';
  })
};
if(listItems.length > 1) {
  button.addEventListener('click', handleClick);
}