js基础总结第二天(基础语句)
js基础总结第二天(基础语句)
一.循环语句
1.基本概念:
2.代码demo
2.1. while语句
let i = 0;
while(i < 100){
console.log(i);
i++;
}
2.2.do-while语句
let i = 0;
do{
console.log(i);
i++;
}while(i < = 100);
2.3.for循环语句
let count = 10;
let i;
for(i = 0; i < count; i++){
console.log(i);
}
2.4.for-in迭代语句
let obj = {
name : "zhangsan",
age : 18,
gender : "male",
};
for(x in obj){
console.log(
obj[x];
);
};
更多for-in的用法请参考:
http://www.nowamagic.net/librarys/veda/detail/1625
2.5.跳转语句
2.5.1 renturn语句
function Add(a,b){
return a + b;
}
let value = Add(1,2);
console.log(value);
更多return用法请参考:http://blog.csdn.net/u013427969/article/details/500523423
2.5.2 break语句
for(var i=1;i<=10;i++){
if(i==6) break;
console.log(i)
}
2.5.3 continue语句
for(var i=1;i<=10;i++){
if(i==6) continue;
console.log(i)
}
2.6 选择语句
2.6.1 if..else 语句
let time = 5;
if(time < 10){
console.log("Good morning");
}else if(time>=10 && time<20){
console.log("Good day");
}else{
console.log("Good evening");
}
2.6.2 switch语句
let day=new Date().getDay();
switch (day)
{
case 0:
console.log("今天是周日");
break;
case 1:
console.log("今天是周一");
break;
case 2:
console.log("今天是周二");
break;
case 3:
console.log("今天是周三");
break;
case 4:
console.log("今天是周四");
break;
case 5:
console.log("今天是周五");
break;
case 6:
console.log("今天是周六");
break:
default:
console.log("超出无五行啦!!");
}
2.6异常处理语句
<p>请输入 5 到 10 之间的数字:</p>
<input type="text" placeholder="请输入一个值" id="demo"></input>
<button type="button" onclick="testFunction()">提交</button>
<p id="mess"></p>
<script type="text/javascript">
function testFunction(){
try{
var iptValue = document.getElementById("demo").value;
if( iptValue=="") throw "值为空";
if(isNaN( iptValue)) throw "不是数字";
if( iptValue > 10) throw "太大";
if( iptValue < 5) throw "太小";
}catch(err){
var altMess=document.getElementById("mess");
altMess.innerHTML="错误:" + err + "。";
}
}
</script>
posted on 2016-09-18 11:30 miaozhenzhong 阅读(138) 评论(0) 编辑 收藏 举报