Math、Date内置对象方法整理

Math : 内置的对象（构造函数）静态属性或静态方法。

                  一、

                        Math.PI : 圆周率

                        console.log(Math.PI);

                  二、近似值

                        1. 四舍五入 ：  Math.round()

                              注: 负数时， <= 0.5   舍去     > 0.5  进一

                              

                              console.log(Math.round(4.5));  //5

                              console.log(Math.round(4.4));   //4

                              console.log(Math.round(-4.5));  //-4

                              console.log(Math.round(-4.5000001)); //-5

                              console.log(Math.round(-4.4)); //-4

                              console.log(Math.round(-4.8)); //-5

                        2. Math.ceil() 向上取整

                              console.log(Math.ceil(4.1)); //5

                              console.log(Math.ceil(4.9)); //5

                              console.log(Math.ceil(-4.1)); //-4

                              console.log(Math.ceil(-4.9)); //-4

                        3. Math.floor() 向下取整

                              console.log(Math.floor(4.1)); //4

                              console.log(Math.floor(4.9)); //4

                              console.log(Math.floor(-4.1)); //-5

                              console.log(Math.floor(-4.9)); //-5

                        4. Math.abs()  取绝对值

                              console.log(Math.abs(3),Math.abs(-3));

                  三、求最值

                        1. Math.max() : 求最大值

                              console.log(Math.max(8,4,2,4,5,2));

                           Math.max.apply(null,数组)

                           var arr = [8,4,2,4,5,2];

                              console.log(Math.max.apply(null,arr));

                        2. Math.min() : 求最小值

                              console.log(Math.min(5,3,2,5,1,3));

                              var arr = [5,3,2,5,1,3];

                              console.log(Math.min.apply(null,arr));

                  四、随机数

                        Math.random() : 0~1之间的随机数，可能包含0，但一定不包含1

                        万能随机公式：

                        Math.floor(Math.random() * (max - min + 1) + min);

                        

                        console.log(randomInt(30,20));

                  

                        function randomInt(min,max){

                              if(min > max){

                                    var t = min;

                                    min = max;

                                    max = t;

                              }

                                                                                    

                              return Math.floor(Math.random() * (max - min + 1) + min);

                                                                              

                        }

                  五、求m的n次方  Math.pow(m,n)

                        onsole.log(Math.pow(2,16));

                  六、求一个数的开方  Math.sqrt()

                        console.log(Math.sqrt(12));

 

Date : 日期对象

                  一、如何创建日期对象？   浏览器显示的 为 外国月份 == 你设置的月份加1  /getFullYear获取到的为原来设置的

                        var date = new Date();

                  二、获取日期时间

                        1. 年： 日期对象.getFullYear()

                        2. 月： 日期对象.getMonth()

                        3. 日： 日期对象.getDate()

                        4. 星期：日期对象.getDay()

                        5. 时:  日期对象.getHours()

                        6. 分: 日期对象.getMinutes()

                        7. 秒 : 日期对象.getSeconds()

                        8. 毫秒: 日期对象.getMilliseconds()

                        9. 时间戳 : 从1970年1月1日0时整到现在的毫秒数。

                              日期对象.getTime()

                  三、设置日期时间

                        1. 年： 日期对象.setFullYear()

                        2. 月： 日期对象.setMonth()

                        3. 日： 日期对象.setDate()

                        4. 时： 日期对象.setHours()

                        5. 分： 日期对象.setMinutes()

                        6. 秒： 日期对象.setSeconds()

                        7. 毫秒: 日期对象.setMilliseconds()

                  四、如何显示本地格式的日期时间

                        日期对象.toLocaleString()    年月日 时分秒

                  五、如何显示本地格式的日期

                        日期对象.toLocaleDateString()      年月日

                  六、如何显示本地格式的时间

                        日期对象.toLocaleTimeString()      时分秒