map,filter,every,some方法,我們分別進(jìn)行舉例//map定義一個(gè)函數用來(lái)遍歷原來(lái)老的數組 var arr = [10,20,5,1000,50]; var newArr = arr.map(function(value, index, array){ return value>10 && value*2 ;//value大于10的時(shí)候才會(huì )乘2 }); console.log(newArr); //filter()定義一會(huì )判斷條件然后把滿(mǎn)足要求的數組選出來(lái) var arr2 = [1,2,3,4,5,6,7,8]; var newArr2 = arr2.filter(function (value,index,array) { return index%2 == 0 || value >5; }); console.log(newArr2); //every()定義一個(gè)判斷條件,然后返回是不是每個(gè)值都都滿(mǎn)足判斷條件 var arr3 = [11,2,3,4,15]; var newArr3 = arr3.every(function (value, index) { return value>1; }); console.log(newArr3); //some()定義一個(gè)判斷條件,然后返回是不是存在一個(gè)值都都滿(mǎn)足判斷條件 var arr4 = [11,2,3,4,15]; var newArr4 = arr4.some(function (value, index) { return value>100; }); console.log(newArr4);
運行結果

//1.圓周率 console.log(Math.PI); //2.向上取整數ceil,向下取整數floor console.log(Math.ceil(Math.PI)); console.log(Math.floor(Math.PI)); //3.取整數,四舍五入 console.log(Math.round(3.4)); console.log(Math.round(3.5)); console.log("======================="); //4.取絕對值 console.log(Math.abs(-3)); console.log(Math.abs(4)); //5.求最大值和最小值 console.log(Math.min(8,245,52,58,2,45,45)); console.log(Math.max(4,5,8,7,6,4)); console.log("=======================") //6.生成隨機數 console.log(Math.random())//0-1之間的隨機數 console.log(Math.random()*10)//0-10之間的隨機數 //假如我們想要3-8之間的隨機數,我們應該怎么辦 //有一個(gè)公式 Math.random() * (y - x) + x //比如我們想要5-9之間的隨機數,那么就是 console.log(Math.random() * (9 - 5) + 5); //7.正余弦 console.log(Math.sin(Math.PI / 2)); console.log(Math.cos(Math.PI / 2));//得到的數值已經(jīng)接近0了 //8.求指數冪pow(),求平方根 console.log(Math.pow(5, 4)); console.log(Math.sqrt(4));
運行結果:

//靜態(tài)成員 var LKTool = { height:function(){ } }; console.log(LKTool.height); //實(shí)例成員 function Dog(name,sex){ this.name = name; this.sex = sex; } var dog = new Dog("xiaoming","male"); console.log(dog.name);
運行結果

https://github.com/ruigege66/JavaScript/blob/master/D22_1_AddedMethod.html https://github.com/ruigege66/JavaScript/blob/master/D22_2_MathObject.htmlhttps://www.cnblogs.com/ruigege0000/聯(lián)系客服