SOURCE

//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
//水仙花数是指一种三位数，其各个数之立方和等于该数。
function printDaffodilNumber() {

    document.write("Print out all daffodil number: " + "<br/>");
    //三位数 100-999
    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 + "<br/>");
document.write("--------------------------------<br/>");