JavaScript 学习笔记（一）prompt、parseInt、document.write、switch(a) {case **:……}、new Date()、getFullYear()

var a=prompt("please type a number:");var b=isNaN(a);document.write("isNan:" + b);

var a=parseInt(prompt("请输入分数："));if(a>=90) {document.write("一");}else if(a>=80) {document.write("二");}else if(a>=70) {document.write("三");}else{document.write("四");}

var a=prompt("请输入星期几：");switch(a) {case '星期一':case "星期二":case "星期三":document.write("痛苦");break;case "星期四":case "星期五":document.write("期待");break;case '星期六':case '星期日':document.write("幸福");break;default:document.write("输入错误！");}

for(i=0;i<4;i++) {for(j=0;j<4;j++) {document.write("* ");}document.write("<br />");}

for(i=4;i>0;i--) {for(j=0;j<i;j++) {document.write("* ");}document.write("<br />");}

var a=4;for(i=0;i<4;i++) {for(j=0;j<a;j++) {document.write("* ");}document.write("<br />");a--;}

for(i=0;i<3;i++) {for(j=0;j<2*(i+1)-1;j++) {document.write("* ");}document.write("<br />");}/*body{text-align:center;}*/

var now=new Date();//var year=new getYear();var year=now.getFullYear();var month=now.getMonth() + 1;var day=now.getDate();var hour=now.getHours();var minute=now.getMinutes();var second=now.getSeconds();document.write(year + "年" + month + "月" + day + "日  " + hour + "时" + minute + "分" + second + "秒");

function checknum() {    var a=prompt("请输入一个数：");    while(isNaN(a)) {        alert("请输入数字！");        var a=prompt("请输入一个数：");    }    if(a%2==0) {        alert("偶数");    }else {        alert("奇数");    }}//<input type="button" value="检查" onclick="checknum()" />