介绍js 的对象 数组以及一些常用的方法
//console.log(); 打印日志 也可以用alert() var book={ name:"java", author:"gzm" }; book.topic="topic1"; console.log(book.name); //js 数据 对象 var primes =[2,3,5,7]; console.log(primes[0]); var points=[{x:0,y:1},{x:0,y:2}]; console.log(points[0].x); var data ={trial1:[[3,4],[1,2]],trial2:[[21,22],[23,24]]}; console.log(data.trial1[1][1]); //js方法声明 及调用 function plus1(x){ return x+1; } console.log(plus1(3)); var x=2; var square = function(x){return x*x;}; <p>console.log(square(x));</p> //js给数据赋值 翻转 var a= []; a.push(1,2,3,4); a.reverse(); <pre name="code" class="javascript">console.log(a); //计算亮点之间的距离 以及this的使用 var points=[{x:0,y:1},{x:0,y:2}]; points.dist =function(){ var p1=this[0]; var p2 = this[1]; var a= p1.x- p2.x; var b = p1.y - p2.y; return Math.sqrt(a*a+b*b); }; console.log(points.dist()); //计算绝对值 function abs(x){ if(x>=0){ return x; }else{ return -x; } } console.log(abs(-2)); // 递归计算阶乘函数 function factoral(n){ var product =1 ; while(n>1){ product*=n; n--; } return product; } console.log(factoral(5)); //循环计算阶乘 function factoria2(n){ var i,product =1; for(i=2;i<=n;i++){ product*=i; } return product; } console.log(factoria2(5));
javaScript 定义一个类标识2D平面几何中的点
function Point(x,y){ this.x=x; this.y=y; } var p = new Point(1,1); Point.prototype.r=function(){ return Math.sqrt(this.x*this.x +this.y*this.y); }; console.log(p.r());