13个JavaScript一行代码技巧，提升开发效率与专业感

const randomBoolean = () => Math.random() >= 0.5;
console.log(randomBoolean());

const isWeekday = (date) => date.getDay() % 6 !== 0;

console.log(isWeekday(new Date(2021, 7, 6)));
// true  因为是周五

console.log(isWeekday(new Date(2021, 7, 7)));
// false 因为是周六

const reverse = str => str.split('').reverse().join('');
reverse('hello world');     
// 'dlrow olleh'

const isBrowserTabInView = () => document.hidden;
isBrowserTabInView();

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("当前页面是否被隐藏：" + document[hidden])

const isEven = num => num % 2 === 0;
console.log(isEven(2));
// true
console.log(isEven(3));
// false

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()));
// 打印当前的时间

const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);
// 事例
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

const elementIsInFocus = (el) => (el === document.activeElement);
elementIsInFocus(anyElement)
// 如果在焦点中返回true，如果不在焦点中返回 false

const touchSupported = () => {
  ('ontouchstart' in window || window.DocumentTouch && document instanceof window.DocumentTouch);
}
console.log(touchSupported());
// 如果支持触摸事件，将返回true，如果不支持则返回false。

const isAppleDevice = /Mac|iPod|iPhone|iPad/.test(navigator.platform);
console.log(isAppleDevice);

const goToTop = () => window.scrollTo(0, 0);
goToTop();

const average = (...args) => args.reduce((a, b) => a + b) / args.length;
average(1, 2, 3, 4);
// 2.5

const celsiusToFahrenheit = (celsius) => celsius * 9/5 + 32;
const fahrenheitToCelsius = (fahrenheit) => (fahrenheit - 32) * 5/9;
// 事例
celsiusToFahrenheit(15);    // 59
celsiusToFahrenheit(0);     // 32
celsiusToFahrenheit(-20);   // -4
fahrenheitToCelsius(59);    // 15
fahrenheitToCelsius(32);    // 0