JS权威指南-概述学习

 1 <script src="/javascripts/application.js" type="text/javascript" charset="utf-8" async defer> 2 ????//对象中嵌套数组（该对象有两个数组元素） 3 ????var a ={ 4 ????????arr1:[[1,2],[3,4]], 5 ????????arr2:[[5,6],[7,8]] 6 ????} ????7 ????//数组中嵌套对象（该数组有两个对象元素） 8 ????var arr1 =[ 9 ????????{obj1:0,obj2:0},10 ????????{obj1:1,obj2:1}11 ????]12 13 ????//对象加上函数，函数就成了方法,每个对象都有方法14 ????var arr1=[]; ???????//定义一个空的数组15 ????arr2.push(1,2,3); ???????//push()方法，向数组中添加元素16 ????arr2.reverse(); ???????//reverse()方法，反转数组元素的次序17 18 ????//我们也可以自定义方法，"this"是对定义方法对象的引用,arr1对象引用19 ????points.dist = function(){ ??????//定义一个方法用来计算两点之间的距离20 ????????var p1=this[0]; ???????????????//通过this获得对当前数组的引用21 ????????var p2=this[1]; ???????????????//并取得数组元素22 ????????var a=p2.x-p1.x; ???????????//X轴上的距离23 ????????var b=p2.y-p1.y; ???????????//Y轴上的距离24 ????????return Math.sqrt(a*a+我们称为b*b);//勾股定理，Math.sqrt()方法计算平方根25 ????};26 ????points.dist() ???????????????????//=>1.414:求得两点之间的距离27 </script>

 1 <script src="/javascripts/application.js" type="text/javascript" charset="utf-8" async defer> 2 ????//JS控制语句 3 ????function abs(x){ 4 ????????if (x>=0) { 5 ????????????return x; ????????????// 1、求绝对值 6 ????????} else { 7 ????????????return -x; 8 ????????} 9 ????}10 11 ????function factorial(n){12 ????????var product=1;13 ????????while (n>1) {14 ????????????product*=n;15 ????????????n--; ?????????????// 2、求阶乘16 ????????}return product;17 ????}18 ????factorial(4); ?????????//=>2419 20 ????function factorial2(n){21 ????????var i,product=1;22 ????????for (var i = 2; i <= n; i++) {23 ????????product*=i;24 ????????return product;25 ????}26 ????factorial2(4); ???//=>2427 28 ????//定义一个类来表示2D平面几何中的点29 </script>