JavaScript技巧汇总

字符串技巧
1、比较时间

const time1 = "2022-03-02 09:00:00";
const time2 = "2022-03-02 09:00:01";
const overtime = time1 < time2;
// overtime => true

2、格式化money

const ThousandNum = num => num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
const money = ThousandNum(1000000);
// money => '1,000,000'

3、生成随机ID

const RandomId = len => Math.random().toString(36).substr(3, len);
const id = RandomId(10);
// id => "xdeguewg1f"

4、生成随机 HEX 颜色值

const RandomColor = () => "#" + Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0");
const color = RandomColor();
// color => "#2cbf89"

5、Generate star ratings

const StartScore = rate => "★★★★★☆☆☆☆☆".slice(5 - rate, 10 - rate);
const start = StartScore(3);
// start => '★★★☆☆'

6、网址查询参数

const params = new URLSearchParams(location.search.replace(/\?/ig, "")); // location.search = "?name=test&sex=man"
params.has("test"); // true
params.get("sex"); // "man"

数字技能
7、Arrangement

用 Math.floor() 代替正数，用 Math.ceil() 代替负数

const num1 = ~~ 1.19;
const num2 = 2.29 | 0;
const num3 = 3.09 >> 0;
// num1 num2 num3 => 1 2 3

8、零填充

const FillZero = (num, len) => num.toString().padStart(len, "0");
const num = FillZero(1234, 5);
// num => "01234"

9、转数

仅对 null、“”、false、数字字符串有效

const num1 = +null;
const num2 = +"";
const num3 = +false;
const num4 = +"169";
// num1 num2 num3 num4 => 0 0 0 169

10、时间戳

const timestamp = +new Date("2022-03-22");
// timestamp => 1647907200000

11、精确小数

const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
const num = RoundNum(1.2345, 2);
// num => 1.23

12、平价

const OddEven = num => !!(num & 1) ? "odd" : "even";
const num = OddEven(2);
// num => "even"

13、取最小值最大值

const arr = [0, 1, 2, 3];
const min = Math.min(...arr);
const max = Math.max(...arr);
// min max => 0 3

14、生成范围随机数

const RandomNum = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
const num = RandomNum(1, 10); // 5

布尔技能
15、短路运算符

const a = d && 1; // Fake operation, judge from left to right, return a false value when encountering a false value, and no longer execute it later, otherwise return the last true value
const b = d || 1; // Take the true operation, judge from left to right, return the true value when encountering the true value, and do not execute it later, otherwise return the last false value
const c = !d; // Returns false if a single expression converts to true, otherwise returns true

16、确定数据类型

可确定的类型：undefined、null、string、number、boolean、array、object、symbol、date、regexp、function、asyncfunction、arguments、set、map、weakset、weakmap

function DataType(tgt, type) {
    const dataType = Object.prototype.toString.call(tgt).replace(/\[object (\w+)\]/, "$1").toLowerCase();
    return type ? dataType === type : dataType;
}
DataType("test"); // "string"
DataType(20220314); // "number"
DataType(true); // "boolean"
DataType([], "array"); // true
DataType({}, "array"); // false

17、检查数组是否为空

const arr = [];
const flag = Array.isArray(arr) && !arr.length;
// flag => true

18、满足条件时执行

const flagA = true; // Condition A
const flagB = false; // Condition B
(flagA || flagB) && Func(); // Execute when A or B is satisfied
(flagA || !flagB) && Func(); // Execute when A is satisfied or B is not satisfied
flagA && flagB && Func(); // Execute when both A and B are satisfied
flagA && !flagB && Func(); // Execute when A is satisfied and B is not satisfied

19、如果非假则执行

const flag = false; // undefined、null、""、0、false、NaN
!flag && Func();

20、数组不为空时执行

const arr = [0, 1, 2];
arr.length && Func();

21、对象不为空时执行

const obj = { a: 0, b: 1, c: 2 };
Object.keys(obj).length && Func();