13 JavaScript one liners make you look like an expert
- 2021-11-13 06:16:20
- OfStack
1. Get a random Boolean value (true/false)
This function uses the
Math.random()
Method returns 1 Boolean value (
true
Or f
alse
). Math. random creates a random number between 0 and 1, and we only need to check whether it is higher or lower than 0.5, and we have a 50% chance of getting true or false.
const randomBoolean = () => Math.random() >= 0.5;
console.log(randomBoolean());
2. Check whether the date provided is a working day
Using this method, we can check whether the date provided in the function is a working day or a weekend day.
const isWeekday = (date) => date.getDay() % 6 !== 0;
console.log(isWeekday(new Date(2021, 7, 6)));
// true Because it's Zhou 5
console.log(isWeekday(new Date(2021, 7, 7)));
// false Because it's Zhou 6
3. Invert the string
There are several different ways to reverse a string. This is the simplest one, using the split (), reverse (), and join () methods.
const reverse = str => str.split('').reverse().join('');
reverse('hello world');
// 'dlrow olleh'
4. Check whether the current tag is hidden
Document.hidden
(Read-only property) returns a Boolean value indicating that the page is (
true
) No (
false
) Hide.
const isBrowserTabInView = () => document.hidden;
isBrowserTabInView();
Off-site: I inadvertently discovered that the playing time of iQiyi advertisement will be counted down when the current tab is activated. When I leave the current tab, the countdown stops and Baidu 1 finds it
document.hidden
This thing.
document.hidden
There is a compatibility problem when h5 is newly added to api.
var hidden
if (typeof document.hidden !== "undefined") {
hidden = "hidden";
} else if (typeof document.mozHidden !== "undefined") {
hidden = "mozHidden";
} else if (typeof document.msHidden !== "undefined") {
hidden = "msHidden";
} else if (typeof document.webkitHidden !== "undefined") {
hidden = "webkitHidden";
}
console.log(" Whether the current page is hidden: " + document[hidden])
5. Check whether a number is even or odd
const isEven = num => num % 2 === 0;
console.log(isEven(2));
// true
console.log(isEven(3));
// false
6. Get time from 1 date
const timeFromDate = date => date.toTimeString().slice(0, 8);
console.log(timeFromDate(new Date(2021, 0, 10, 17, 30, 0)));
// "17:30:00"
console.log(timeFromDate(new Date()));
// Print the current time
7. Keep the n decimal
const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);
// Examples
toFixed(25.198726354, 1); // 25.1
toFixed(25.198726354, 2); // 25.19
toFixed(25.198726354, 3); // 25.198
toFixed(25.198726354, 4); // 25.1987
toFixed(25.198726354, 5); // 25.19872
toFixed(25.198726354, 6); // 25.198726
8. Check if any elements are currently in focus
We can use
document.activeElement
Property to check whether an element is currently in focus.
const elementIsInFocus = (el) => (el === document.activeElement);
elementIsInFocus(anyElement)
// If you return in focus true If not in focus, return false
9. Check whether the current browser supports touch events
const touchSupported = () => {
('ontouchstart' in window || window.DocumentTouch && document instanceof window.DocumentTouch);
}
console.log(touchSupported());
// If touch events are supported, the true Or return if it is not supported false .
10. Check whether the current browser is on an Apple device
const isWeekday = (date) => date.getDay() % 6 !== 0;
console.log(isWeekday(new Date(2021, 7, 6)));
// true Because it's Zhou 5
console.log(isWeekday(new Date(2021, 7, 7)));
// false Because it's Zhou 6
11. Scroll to the top of the page
const isWeekday = (date) => date.getDay() % 6 !== 0;
console.log(isWeekday(new Date(2021, 7, 6)));
// true Because it's Zhou 5
console.log(isWeekday(new Date(2021, 7, 7)));
// false Because it's Zhou 6
12. Get the average value of the parameter
const isWeekday = (date) => date.getDay() % 6 !== 0;
console.log(isWeekday(new Date(2021, 7, 6)));
// true Because it's Zhou 5
console.log(isWeekday(new Date(2021, 7, 7)));
// false Because it's Zhou 6
13. Fahrenheit/Celsius conversion
const celsiusToFahrenheit = (celsius) => celsius * 9/5 + 32;
const fahrenheitToCelsius = (fahrenheit) => (fahrenheit - 32) * 5/9;
// Examples
celsiusToFahrenheit(15); // 59
celsiusToFahrenheit(0); // 32
celsiusToFahrenheit(-20); // -4
fahrenheitToCelsius(59); // 15
fahrenheitToCelsius(32); // 0