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2020javaweb教程之JavaScript条件语句以及switch

if…else语句

var date=new Date();

var hours=date.getHours()+10;

document.write("当前时间为"+hours+"点<br>")

if(hours>6&&hours<12){ 
  document.write("早上好"); 



}else if(hours>=12&&hours<14){ 
  document.write("中午好"); 
}else if(hours>=14&&hours<18){
  document.write("下午好");
}else{
  document.write("晚上好");
}

switch语句

var date=new Date();
var day=date.getDay();
document.write("今天")
switch(day){
	case 1:
	document.write("周一");break;
	case 2:
	document.write("周二");break;
	case 3:
	document.write("周三");break;
	case 4:
	document.write("周四");break;
	case 5:
	document.write("周五");break;
	case 6:
	document.write("周六");break;
	default:
	document.write("周日");break;
}

while语句

var i=0;
var sum=0;
while(i<100){
	i++;
	sum+=i;
}
document.write(sum)

do…while语句

var i2=0;
var sum2=0;
do{
	i2++;
	sum2+=i2;
}while(i2<100)
document.write(sum2)

for语句

var sum3=0;
for(var i3=0;i3<=100;i3++){
	sum3+=i3;
}
document.write(sum3)