测开之路九十八：js变量和语句

这里为了方便调试，在jsbin网站上面编写js脚本：https://jsbin.com/?js,console

可以点击增加/减少对应展示分页，Console为控制台部分，Output为页面部分

变量和运算

if语句

switch case

while

do while

for循环

for in

var a = 10;
var b = 20.5;
console.log(typeof a);
console.log(a+b);
console.log(a>b);
console.log(a<b && a>2);

if(typeof a == "number"){
document.write("条件成立");
console.log("条件成立");
}else{
console.log("条件不成立");
}

//switch case
var grade = 'X'
switch(grade)
{
case "A": document.write("成绩为A");
break;

case "B": document.write("成绩为B");
break;

case "C": document.write("成绩为C");
break;

default: document.write("未知成绩");

}

//while
var count = 0;
while (count < 10){
document.write("当前值是：" + count + "<br />");
count++;
}
document.write("循环结束")

//do while
var count = 0;
do{
document.write("当前值是：" + count + "<br />");
count++;
}
while(count < 10)

//for
for(var i=1; i<10; i++){
document.write("当前值是：" + i + "<br />");

//嵌套
if(i == 8){
break;
}
}
document.write("循环结束");

//for in
var values = ["a", "b", "c", "d"];
for (value in values){
//遍历索引
document.write("当前索引是：" + value + "<br />");

//遍历值
document.write("当前值是：" + values[value] + "<br />");
}
document.write("循环结束");