'let' is block-scoped; 'const' is function-scoped.

'let' cannot be redeclared; 'const' can be redeclared.

'let' is used for constants; 'const' is for variables.

'let' allows reassignment; 'const' does not.

document.selectElementById('yourElementId')

getElementById('yourElementId')

document.getElementById('yourElementId')

document.querySelector('#yourElementId')

element.className.append('new-class');

element.addClass('new-class');

element.classList.add('new-class');

element.classList.insert('new-class');

Return false in the event handler function.

Use event.preventDefault() in the event handler.

Use event.stopPropagation() in the event handler.

Call event.cancelBubble() to stop the event.

A function expression is a type of variable declaration in JavaScript.

A function expression is a built-in JavaScript method for creating objects.

A function expression is a function defined within an expression, often assigned to a variable.

A function expression is a function that cannot be assigned to a variable.

By including them in the parentheses during function definition or call.

By using global variables to store values.

By passing them as return values from another function.

By defining them as constants outside the function.

To optimize code performance and speed up execution.

To define variables and manage their scope effectively.

To handle exceptions and prevent program crashes.

To create loops and iterate over data structures.

throw Error('Custom error');

throw 'This is an error';

throw new Exception('Error message');

throw new Error('Your custom error message');

Synchronous functions block execution until complete, while asynchronous functions allow concurrent execution.

Synchronous functions run in parallel, while asynchronous functions run sequentially.

Asynchronous functions block execution until they are finished, unlike synchronous functions.

Synchronous functions are faster than asynchronous functions in all cases.

Invoke document.newElement('tagName') to add an element to the DOM.

Call document.insertElement('tagName') to create a new node.

Use document.addElement('tagName') to insert a new element.

Use document.createElement('tagName') to create a new element and append it to the DOM.

The 'this' keyword in JavaScript refers to the current execution context, which can vary based on how a function is called.

The 'this' keyword is a reserved word that cannot be used in JavaScript.

The 'this' keyword is used to define constants in JavaScript.

The 'this' keyword always refers to the global object in JavaScript.

element.removeListener('eventType', functionReference);

element.deleteEventListener('eventType', functionReference);

element.removeEventListener('eventType', functionReference);

element.detachEvent('eventType', functionReference);

A callback function is a function passed to another function to be executed later, often used for handling asynchronous operations.

A callback function is a method that runs in the background without user input.

A callback function is a function that cannot be executed until the program ends.

A callback function is a type of variable used to store data.

17

1025

25

107