CodeSnippet-JS

约 387 字大约 1 分钟

2024-03-16

箭头函数

 let sayHi = () => alert("Hello!"); //无参数：
 let sum = (a, b) => a + b; //等价 let sum = function(a, b) {  return a + b;};
 let sum = (a, b) => {  // 花括号打开多线功能
   let result = a + b;
   return result; // 如果我们使用花括号，使用返回来获得结果
 };

时间

时间格式化

//const formatYmd = (date) => date.toISOString().slice(0, 10);
new Date().toISOString().slice(0, 10);
//formatYmd(new Date()); // 2020-05-06

获得年月日时分秒

new Date().toISOString().split(/[^0-9]/).slice(0, -1);
// ['2022', '06', '11', '09', '53', '16', '808']

数组

获取数组中随机几项

const randomItems = (arr, count) => arr.concat().reduce((p, _, __, arr) => (p[0] < count ? [p[0] + 1, p[1].concat(arr.splice((Math.random() * arr.length) | 0, 1))] : p), [0, []])[1];
//randomItems([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 3); // [4, 8, 5]
//randomItems(['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'], 4); // ['e', 'c', 'h', 'j']

数组去重

	const nums = [1, 2, 2, 3, 1, 2, 4, 5, 4, 2, 6];
	[...new Set(nums)] // [1, 2, 3, 4, 5, 6]

for循环

	for (let prop in ['a', 'b', 'c'])
  		console.log(prop);            // 0, 1, 2 (in 数组的索引)

  	for (let prop of ['a', 'b', 'c'])
  		console.log(prop);            // a, b, c (of 数组值)

  	['a', 'b', 'c'].forEach(
  		val => console.log(val)     // a, b, c (array values)
);

序列化指定字段

	const user = {
	  id: 1234,
	  username: 'johnsmith',
	  name: 'John Smith',
	  age: 39
	};

	JSON.stringify(user, ['username', 'name']);
	// '{ "username": "johnsmith", "name": "John Smith" }'

字符串

随机字符串

	const randomString = () => Math.random().toString(36).slice(2);

展开语法

	let arr1 = [0, 1, 2];
	let arr2 = [3, 4, 5];

	arr1 = [...arr2, ...arr1];
	//  arr1 is now [3, 4, 5, 0, 1, 2]

检查是否是数字

const isNumber = (value) => !isNaN(parseFloat(value)) && isFinite(value);