Advanced JavaScript DOM Coding Examples

How do you add an event listener to an element in JavaScript?
What is the difference between innerHTML and textContent in JavaScript?
How do you create a new element in the DOM using JavaScript?
What is the difference between childNodes and children in JavaScript?
How do you remove an element from the DOM using JavaScript?
How do you check if an element has a specific class using JavaScript?
How do you get the value of a form input using JavaScript?
How do you set the value of a form input using JavaScript?
How do you get the value of a selected option in a select element using JavaScript?
How do you create an HTML table dynamically using JavaScript?

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How do you add an event listener to an element in JavaScript?

const button = document.querySelector(‘button’);

button.addEventListener(‘click’, () => {

  console.log(‘Button clicked’);

});

Explanation:

To add an event listener to an element in JavaScript, you can use the addEventListener method on the element and pass in the event type (e.g. ‘click’, ‘mousemove’, etc.) and a callback function that will be executed when the event is triggered.

What is the difference between innerHTML and textContent in JavaScript?

const element = document.querySelector(‘#my-element’);

element.innerHTML = ‘<b>Hello</b>’; // renders ‘Hello’ in bold

element.textContent = ‘<b>Hello</b>’; // renders ‘<b>Hello</b>’ as plain text

Explanation:

innerHTML sets or gets the HTML content inside an element, including any HTML tags and their attributes, while textContent sets or gets the text content of an element, stripping out any HTML tags.

How do you create a new element in the DOM using JavaScript?

const parent = document.querySelector(‘#parent-element’);

const child = document.createElement(‘div’);

child.textContent = ‘Hello, world!’;

parent.appendChild(child);

Explanation:

To create a new element in the DOM using JavaScript, you can use the createElement method on the document object and pass in the name of the element you want to create. You can then set any attributes or content on the new element and add it to the DOM using methods like appendChild or insertBefore.

What is the difference between childNodes and children in JavaScript?

const parent = document.querySelector(‘#parent-element’);

console.log(parent.childNodes); // returns a NodeList containing all child nodes, including text nodes

console.log(parent.children); // returns an HTMLCollection containing only element nodes

Explanation:

childNodes returns a NodeList containing all child nodes, including text nodes and comment nodes, while children returns an HTMLCollection containing only the element nodes.

How do you remove an element from the DOM using JavaScript?

const element = document.querySelector(‘#my-element’);

element.remove();

Explanation:

To remove an element from the DOM using JavaScript, you can use the remove method on the element. This will remove the element and all of its child nodes from the DOM.

How do you check if an element has a specific class using JavaScript?

const element = document.querySelector(‘#my-element’);

if (element.classList.contains(‘my-class’)) {

  console.log(‘Element has class “my-class”‘);

}

Explanation:

To check if an element has a specific class using JavaScript, you can use the classList.contains method on the element and pass in the name of the class you want to check for.

How do you get the value of a form input using JavaScript?

const input = document.querySelector(‘#my-input’);

console.log(input.value);

Explanation:

To get the value of a form input using JavaScript, you can use the value property on the input element.

How do you set the value of a form input using JavaScript?

const input = document.querySelector(‘#my-input’);

input.value = ‘Hello, world!’;

Explanation:

To set the value of a form input using JavaScript, you can use the value property on the input element and assign it a new value.

How do you get the value of a selected option in a select element using JavaScript?

const select = document.querySelector(‘#my-select’);

console.log(select.value);

Explanation:

To get the value of a selected option in a select element using JavaScript, you can use the value property on the select element.

How do you create an HTML table dynamically using JavaScript?

const data = [

  { name: ‘John’, age: 25 },

  { name: ‘Jane’, age: 30 },

  { name: ‘Bob’, age: 40 },

];

const table = document.createElement(‘table’);

const headerRow = document.createElement(‘tr’);

const headerNames = [‘Name’, ‘Age’];

// Create header cells

headerNames.forEach((headerName) => {

  const headerCell = document.createElement(‘th’);

  headerCell.textContent = headerName;

  headerRow.appendChild(headerCell);

});

// Add header row to table

table.appendChild(headerRow);

// Create data rows

data.forEach((row) => {

  const dataRow = document.createElement(‘tr’);

  // Create cells for each property

  Object.values(row).forEach((cellValue) => {

    const dataCell = document.createElement(‘td’);

    dataCell.textContent = cellValue;

    dataRow.appendChild(dataCell);

  });

  // Add data row to table

  table.appendChild(dataRow);

});

// Add table to the DOM

document.body.appendChild(table);

Explanation:

To create an HTML table dynamically using JavaScript, you can use the createElement method on the document object to create the necessary table, row, and cell elements. You can then populate the table with data from an array or other data source using loops and conditional statements to create the necessary table cells and rows. Finally, you can add the table to the DOM using methods like appendChild or insertBefore.