1.格式化金钱值1.格式化金钱值
const ThousandNum = num => num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
const money = ThousandNum(20210214);
// money => "20,190,214"
const ThousandNum = num => num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
const money = ThousandNum(20210214);
// money => "20,190,214"2.取整代替正数的Math.floor()，代替负数的Math.ceil()2.取整代替正数的Math.floor()，代替负数的Math.ceil()
const num1 = ~~ 1.69;
const num2 = 1.69 | 0;
const num3 = 1.69 >> 0;
// num1 num2 num3 => 1 1 1
const num1 = ~~ 1.69;
const num2 = 1.69 | 0;
const num3 = 1.69 >> 0;
// num1 num2 num3 => 1 1 13.转数值只对null、""、false、数值字符串有效3.转数值只对null、""、false、数值字符串有效
const num1 = +null;
const num2 = +"";
const num3 = +false;
const num4 = +"169";
// num1 num2 num3 num4 => 0 0 0 169
const num1 = +null;
const num2 = +"";
const num3 = +false;
const num4 = +"169";
// num1 num2 num3 num4 => 0 0 0 1694.精确小数4.精确小数
const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
const num = RoundNum(1.69, 1);
// num => 1.7
const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
const num = RoundNum(1.69, 1);
// num => 1.75.取最小最大值5.取最小最大值
const arr = [0, 1, 2];
const min = Math.min(...arr);
const max = Math.max(...arr);
// min max => 0 2
const arr = [0, 1, 2];
const min = Math.min(...arr);
const max = Math.max(...arr);
// min max => 0 26.是否为空对象6.是否为空对象
const obj = {};
const flag = DataType(obj, "object") && !Object.keys(obj).length;
// flag => true
const obj = {};
const flag = DataType(obj, "object") && !Object.keys(obj).length;
// flag => true7.判断数据类型7.判断数据类型
function DataType(tgt, type) {
const dataType = Object.prototype.toString.call(tgt).replace(/\[object (\w+)\]/, "$1").toLowerCase();
return type ? dataType === type : dataType;
}
DataType("liner"); // "string"
DataType(2021630); // "number"
DataType(true); // "boolean"
DataType([], "array"); // true
DataType({}, "array"); // false
function DataType(tgt, type) {
const dataType = Object.prototype.toString.call(tgt).replace(/\[object (\w+)\]/, "$1").toLowerCase();
return type ? dataType === type : dataType;
}
DataType("liner"); // "string"
DataType(2021630); // "number"
DataType(true); // "boolean"
DataType([], "array"); // true
DataType({}, "array"); // false8.克隆数组8.克隆数组
const _arr = [0, 1, 2];
const arr = [..._arr];
// arr => [0, 1, 2]
const _arr = [0, 1, 2];
const arr = [..._arr];
// arr => [0, 1, 2]9.合并数组9.合并数组
const arr1 = [0, 1, 2];
const arr2 = [3, 4, 5];
const arr = [...arr1, ...arr2];
// arr => [0, 1, 2, 3, 4, 5];
const arr1 = [0, 1, 2];
const arr2 = [3, 4, 5];
const arr = [...arr1, ...arr2];
// arr => [0, 1, 2, 3, 4, 5];10.去重数组10.去重数组
const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]
const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]11.截断数组11.截断数组
const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]
const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]12.交换赋值12.交换赋值
let a = 0;
let b = 1;
[a, b] = [b, a];
// a b => 1 0
let a = 0;
let b = 1;
[a, b] = [b, a];
// a b => 1 013.克隆对象13.克隆对象
const _obj = { a: 0, b: 1, c: 2 }; // 以下方法任选一种(本人偏爱第一种，简单明了，与克隆数组几乎一样)
const obj = { ..._obj };
const obj = JSON.parse(JSON.stringify(_obj));
// obj => { a: 0, b: 1, c: 2 }
const _obj = { a: 0, b: 1, c: 2 }; // 以下方法任选一种(本人偏爱第一种，简单明了，与克隆数组几乎一样)
const obj = { ..._obj };
const obj = JSON.parse(JSON.stringify(_obj));
// obj => { a: 0, b: 1, c: 2 }14.合并对象14.合并对象
const obj1 = { a: 0, b: 1, c: 2 };
const obj2 = { c: 3, d: 4, e: 5 };
const obj = { ...obj1, ...obj2 };
// obj => { a: 0, b: 1, c: 3, d: 4, e: 5 }
const obj1 = { a: 0, b: 1, c: 2 };
const obj2 = { c: 3, d: 4, e: 5 };
const obj = { ...obj1, ...obj2 };
// obj => { a: 0, b: 1, c: 3, d: 4, e: 5 }为什么 obj 不是 {a:0,b:1,c:2,d:4,e:5}而是上面结果 下面相同的例子就可以说明