一行JS代码

• 获取一个随机布尔值

const randomBoolean = () => Math.random() >= 0.5;
console.log(randomBoolean());
// true:50%; false:50%

• 检查日期是否为工作日

const isWeekday = (date) => date.getDay() % 6 !== 0;
console.log(isWeekday(new Date(2021, 0, 11)));
// true (Monday)
console.log(isWeekday(new Date(2021, 0, 10)));
//  false (Sunday)

• 反转字符串

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

• 检查当前 Tab 页是否在前台

const isBrowserTabInView = () => document.hidden;
isBrowserTabInView();
// Result: returns true or false depending on if tab is in view / focus

• 检查数字是否为奇数

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

• 从日期中获取时间

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()));
//当前时间

• 保留小数点（非四舍五入）

const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);
// Examples
toFixed(36.745896214, 1);       // 36.7
toFixed(36.745896214, 2);       // 36.74
toFixed(36.745896214, 3);       // 36.745
toFixed(36.745896214, 4);       // 36.7458
toFixed(36.745896214, 5);       // 36.74589
toFixed(36.745896214, 6);       // 36.745896

• 检查元素当前是否为聚焦状态

const elementIsInFocus = (el) => (el === document.activeElement);
elementIsInFocus(anyElement)
//true -获焦，false -不是获焦

• 检查浏览器是否支持触摸事件

const touchSupported = () => {
  ('ontouchstart' in window || window.DocumentTouch && document instanceof window.DocumentTouch);
}
console.log(touchSupported());
// Result: will return true if touch events are supported, false if not

• 检查当前用户是否为苹果设备

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

• 滚动到页面顶部

// IE 不支持 scrollTo() 方法
const goToTop = () => window.scrollTo(0, 0);
goToTop();

• 获取所有参数平均值

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

• 转换华氏度/摄氏度

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