精通JavaScript前70面总结

<script language="javascript">/*//变量的优先级别var scope = "globle variable";function checkscope() {var scope = "local variable";document.write(scope);}checkscope();//调用函数，输出结果*///javascript没有块级作用域/*function test(q) {var i = 0;if(q == 2) {var j = 0;for(var k = 0;k < 10;k ++) {document.write(k + " ==== ");}    document.write("<br>" + k); //这一段为什么没有执行 ^_^!!!}document.write("<br>" + j);}test(2);*//*var today = new Date(); //new创建对象alert(today);today = null;alert(today);var myArray = ['a','b','c','d'];//创建数组document.write(myArray + "<br>");delete myArray[3];document.write(myArray + "<br>"); //用delete删除对象的属性或移除数组的元素//运算符 () 调用方法*//*//while控制语句document.write("<table border='1'>");var i = 0;while(i < 10) {document.write("<tr>");document.write("<td>");document.write(i);document.write("</td>");document.write("</tr>");i ++;}document.write("</table>");*//*//用for打印乘法表document.write("<table border='1'>");for(var i = 1;i <= 9;i ++) {document.write("<tr>");for(var j = 1; j <= i;j ++) {document.write("<td>");document.write(i + " * " + j + " = " + (j * i));document.write("</td>");}document.write("</tr>");}document.write("</table>");*//*//有返回值的函数调用function getMax(x,y) {//此处不能用var x , var yif(x > y) {return x;} else {return y;}}var m = getMax(1,2);alert(m);*//*//全局变量 ：变量不在函数中//局部变量 ：变量定义在函数中//参数变量可变的函数,argumentsfunction testparams() {var params = "";for(var i = 0;i < arguments.length;i ++) {params += arguments[i];}alert(params);}testparams("liusheng",23);*//*//数值处理函数//parseInt(numString,[radix]) radix是几进制 123abc能转 abc123不能转//假如不能转返回 NaN 要用 isNaN判断 或者是用temp == NaN//document.write(parseInt("ad234",10));function testParse(x) {var temp = parseInt(x);if(temp == NaN) {alert("NaN");} else {alert(temp);}}testParse("123abc");testParse("abc123");*///创建对象 var o = new Object();//o.field = value,假如field本来不存在”类“中,会改变本对象”类“的field//但是不会改变其他对象的field.function Student(name,age,grade) {this.name = name;this.age = age;this.grade = grade;}var s1 = new Student("刘胜",21,0902);alert(s1.name + " " + s1.age + " " + s1.grade);var s2 = new Student("小红",21,0000);s2.class = 7;//alert(s2.name + " " + s2.age + " " + s2.grade);alert(s2.class);</script>