This is somewhat of an extension to last week's 7 Killer One-Liners in JavaScript. If you haven't already read the article, you are highly encouraged to do so.
1. Check if an element is visible in the viewport
IntersectionObserver
is a great way to check if an element is visible in the viewport.
const callback = (entries) => {
entries.forEach((entry) => {
if (entry.isIntersecting) {
// `entry.target` is the dom element
console.log(`${entry.target.id} is visible`);
}
});
};
const options = {
threshold: 1.0,
};
const observer = new IntersectionObserver(callback, options);
const btn = document.getElementById("btn");
const bottomBtn = document.getElementById("bottom-btn");
observer.observe(btn);
observer.observe(bottomBtn);
You can customize the behavior of the observer using the option
parameter. threshold
is the most useful attribute, it defines the percentage of the element that needs to be visible in the viewport for the observer to trigger.
2. Detect device
You can use the navigator.userAgent
to gain minute insights and detect the device running the application
const detectDeviceType = () =>
/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(
navigator.userAgent
)
? "Mobile"
: "Desktop";
console.log(detectDeviceType());
3. Hide elements
You can just toggle the visibility of an element using the style.visibility
property and in case you want to remove it from the render flow, you can use the style.display
property.
const hideElement = (element, removeFromFlow = false) => {
removeFromFlow
? (element.style.display = "none")
: (element.style.visibility = "hidden");
};
If you don't remove an element from the render flow, it will be hidden, but its space will still be occupied. It is highly useful while rendering long lists of elements, the elements NOT in view (can be tested using IntersectionObserver
) can be hidden to provide a performance boost.
4. Get the parameters from the URL
JavaScript makes fetching the parameters
from any address a walk in the park using the URL
object.
const url = new URL(window.location.href);
const paramValue = url.searchParams.get("paramName");
console.log(paramValue);
5. Deep copy an object with ease
You can deep copy
any object by converting it to a string and back to an object.
const deepCopy = (obj) => JSON.parse(JSON.stringify(obj));
6. wait
function
JavaScript does ship with a setTimeout
function, but it does not return a Promise
object, making it hard to use in async functions
. So we have to write our own wait
/sleep
function.
const wait = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
const asyncFunc = async () => {
await wait(1000);
console.log("async");
};
asyncFunc();
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Top comments (2)
Great post, helpful snippets, especially deep cloning an object as opposed to passing by reference.
I'd also recommend the global structuredClone method, which is fairly new and just being rolled out to newer browsers and in Node 17, but if you have access to it, it's a lot better for serialising JavaScript objects like
Map
s!Good bits of information