console 命令行工具 X clear

console

//if单向选择
var a = 100;
if (a > 10) {
   document.write("1");
        }

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

//if…else…双向选择
var a = 100;
 if (a < 10) {
        document.write("1");} 
    else {
       document.write("2");}
document.write('<br/>---------------<br/>');   

//if…else if…else…多向选择
var score = 480;
        if (score < 400)
        {
            document.write("不读书");    
        }
        else if (score >=400 && score < 500)
        {
            document.write("上二本"); 
        }
        else
        {
            document.write("上一本！"); 
        }

document.write('<br/>---------------<br/>');   
//if语句的嵌套
var a = 3;
var b = 10;
        
if (a < 5)
{
    if (b < 5)
    {
        document.write("a<5，b<5");
    }
        else
    {
            document.write("a<5，b>5");
    }
}
else 
    {
        if (b < 5)
        {
            document.write("a>5，b<5");
        }
            else
            {
                document.write("a<5，b>5");
            }
    }


document.write('<br/>---------------<br/>');   
//判断15是不是整数
    function isInteger(num){
        var result = false;
        var num = 15;
        if(parseInt(num) == parseFloat(num)){
           result = true;
        }
         return result;
    }
    if (isInteger(15)){
        document.write("15 is an integer.");
    }
    else{
        document.write("15 isn't an integer.");
    }

document.write('<br/>---------------<br/>');   
//3.24是浮点数
    function isInteger(num){
        var result = false;
        var num = 3.24;
        if(parseInt(num) == parseFloat(num)){
           result = true;
        }
         return result;
    }
    if (isInteger(3.24)){
        document.write("3.24 is an integer.");
    }
    else{
        document.write("3.24 is a decimals.");
    }


document.write('<br/>---------------<br/>');   
function printDaffodilNum() {
    document.write("Print daffiodil number: "+"<br/>");
    for(var num = 100; num <1000 ; num++) {
        var unitsDigit = num % 10;
        var tensDigit = parseInt((num / 10) % 10);
        var hundredsDigit = parseInt(num / 100);

        //如果是水仙花数，则打印
        if(num==(unitsDigit*unitsDigit*unitsDigit+tensDigit*tensDigit*tensDigit+hundredsDigit*hundredsDigit*hundredsDigit)){
					document.write(num+"<br/>");
				}
    }
}
printDaffodilNum();
document.write('---------------<br/>');

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        //var $a = 3;
        //var a;
        //var myString = 'Heather';
        //var noSpace = null;
        //var isReal = true;

        //document.write($a + '<br/>');
        //document.write(myString + '<br/>');
        //document.write(noSpace + '<br/>');
        //document.write(isReal + '<br/>');
       
    </script>
</head>
<body>
</body>
</html>