To use an HTML class in JavaScript, you can use the getElementsByClassName method. This method returns an array-like object called a NodeList containing all elements in the document that have the specified class name. You can then access individual elements using their index. Here's an example:

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// HTML code
<div class="my-class">Hello World!</div>

// JavaScript code
const elements = document.getElementsByClassName("my-class");
console.log(elements[0].textContent); // outputs "Hello World!"

In the example above, we use getElementsByClassName to select the HTML element with the class name "my-class". We then log the text content of the first element (since getElementsByClassName returns a NodeList).

getElementsByName is a method in JavaScript that allows you to select all elements in the DOM with a specific name attribute. It returns a NodeList object, which is similar to an array, containing all the selected elements.

Here's an example of how you can use getElementsByName in JavaScript:

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// HTML code
<input type="text" name="myInput">

// JavaScript code
const inputElements = document.getElementsByName('myInput');
console.log(inputElements); // NodeList [input]

In this example, getElementsByName is used to select the input element with the name attribute equals to 'myInput'. The method returns a NodeList object containing this element, which is then stored in the inputElements variable. The console.log statement displays the NodeList object in the browser console.

To do a query selector for the same h1, you can use the querySelectorAll() method and pass it the h1 tag as the parameter. Then, you can use a loop to go through each h1 element in the NodeList result and create a prompt for each one. Here's an example in JavaScript:

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const headings = document.querySelectorAll("h1");

for(let i = 0; i < headings.length; i++) {
  const userInput = prompt(`Enter something for ${headings[i].textContent}`);
  headings[i].textContent = userInput; // update the heading with the user input
}

This code selects all the h1 elements in the document and loops through each one. For each h1 element, it creates a prompt that asks the user to enter something for that heading, and then updates the heading with the user's input.

Note that if you have more than one h1 element in the document, this code will prompt the user multiple times.

document.querySelectorAll is a method in JavaScript used to select a group of elements in the Document Object Model (DOM) based on a CSS selector. It returns a static NodeList containing all elements that match the specified selector. It is useful for manipulating multiple elements at a time.

For example, if you wanted to change the background colour of every element with a particular class in your HTML, you could do something like this:

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let elementList = document.querySelectorAll('.my-class');

for (let element of elementList) {
  element.style.backgroundColor = '#F00';
}