console 命令行工具 X clear

console

//选择结构:if
var a=1;
var b=2;
var c=3;
var d=4;
//单向选择：if…
if(a<b){
    document.write(a+"<br/>");
}
//双向选择：if…else…
if(a>b){
    document.write(a+"<br/>");
}
else{
    document.write(b+"<br/>");
}
//多向选择：if…else if…else…
if(a>b){
    document.write(a+"<br/>");
}
else if(a<b){
    document.write(b+"<br/>");
}
else{
    document.write(c+"<br/>");
}
//if语句的嵌套
if(a>b){
    document.write(a+"<br/>");
    if(a<b){
      document.write(b+"<br/>");  
    }
    else{
       document.write(c+"<br/>");  
    }
}
else{
    document.write(d+"<br/>");
}
document.write("--------------------------------<br/>");

// 选择结构：switch
var day = 6;
switch(day){
case 1:
case 2:
case 3:
case 4:
case 5:document.write("工作日"+"<br/>");break;
case 6:
case 7:document.write("休息日"+"<br/>");break;
}
document.write("--------------------------------<br/>");

//循环结构练习
//水仙花数
function printDaffodilNumber() {

    document.write("Print out all daffodil number: " + "<br/>");

    for (var num =100 ; num <1000 ; num++) {
        var unitsDigit = num % 10;
        var tensDigit = parseInt((num / 10) % 10);
        var hundredsDigit = parseInt(num / 100);

        //判断是否是水仙花数，并输出
    if(num==(unitsDigit*unitsDigit*unitsDigit+tensDigit*tensDigit*tensDigit+hundredsDigit*hundredsDigit*hundredsDigit)){
            document.write(num+"<br/>");
        }
    } 
}
printDaffodilNumber(); 
document.write("--------------------------------<br/>");

//判断是否为小数
function isInteger(num) {
    var result = false;
    result=parseInt(num) == parseFloat(num)
    // 判断num是否是整数
    if (result){
        document.write(num+ "不是小数"+"<br/>")
    }

    else{
        document.write(num+ "是小数"+"<br/>")
    }
    return result;
}

isInteger(15);
isInteger(15.15);

document.write("--------------------------------<br/>");

//有返回值
function one(a) {
    var one = a + 1;
    return one;
}
var i = one(1) + 2;
document.write(i);

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
 
</head>
<body>
</body>
</html>