Category: JavaScript Answers

To turn off antialiasing on an HTML canvas element with JavaScript, we can set the imageSmoothingEnabled of the 2d canvas context to false .

For instance, we can write the following HTML:

<canvas width='200' height='200'></canvas>

to add the canvas.

Then we can write:

const c = document.querySelector("canvas");
const ctx = c.getContext("2d");
ctx.imageSmoothingEnabled = false
ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.stroke();

to get the canvas and turn off antialiasing for it with:

ctx.imageSmoothingEnabled = false

We get the canvas element with document.querySelector .

Then we call getContext with '2d' to get the 2d context.

Then we draw a circle in the canvas with:

ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.stroke();

To add a new li element into a ul on click of an element with JavaScript, we can add a click listener to the element we want to click to add the li with.

For instance, if we have:

<button>
  add
</button>
<ul>

</ul>

Then we can write:

const btn = document.querySelector('button')
const ul = document.querySelector('ul')
btn.addEventListener('click', () => {
  const li = document.createElement("li");
  li.appendChild(document.createTextNode("foo"));
  ul.appendChild(li);
})

to add the click listen to the button with JavaScript.

We get the button an ul elements with document.querySelector .

Then we call addEventListener to add a click listen to the btn button.

In the click listener, we create a new li element with document.createElement .

Then we call li.appendChild to add a text node created by the createTextNode method as its content.

And then we call ul.appendChild with li to add the li into the ul .

To display only 10 characters of a long string in JavaScript, we can use the slice method to return the first 10 characters of the string.

For instance, we can write:

const text = "I am too long string";  
const count = 10;  
const result = text.slice(0, count) + (text.length > count ? "..." : "");  
console.log(result)

We have the text string variable.

And then we have the count set to the max number of characters we want in the truncated string.

Next, we create the result truncated string by calling slice with 0 and the count .

And then we add '...' to the end of the string if text.length is bigger than count .

To find the closest parent element to an HTML element in an HTML document without jQuery, we can use the closest method to find the closest parent of the given element.

For instance, if we have the following HTML:

<table>  
  <thead>  
    <tr>  
      <th>head</th>  
    </tr>  
  </thead>  
  <tbody></tbody>  
</table>

Then we can write:

const th = document.querySelector('th')  
console.log(th.closest('thead'));

to get the th element with document.querySelector .

Then we call closest on it with the 'thead' string to get the thead element closest to the th element.

The console log should log the thead element as a result.