SOURCE

var globalVariable1 = 0;

function test1() {
    document.write(localVariable1+ "<br/>");
    var localVariable1 = 2;
    //打印globalVariable1
    document.write(globalVariable1 + "<br/>");

    //打印localVariable1
    document.write(localVariable1+ "<br/>");
}

//打印localVariable1
//document.write(localVariable1);

//打印globalVariable2
document.write(globalVariable2 + "<br/>");


test1();

var globalVariable2 = 1;

function test2() {
    var localVariable2 = 3;

    //打印localVariable1
    //document.write(localVariable1 + "<br/>");

}
test2();

//打印localVariable2
//document.write(localVariable2 + "<br/>");
//打印globalVariable1
document.write(globalVariable1 + "<br/>"); 

function isLeapYear(year) 
{
    //判断闰年的条件
    if ((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0)) 
    {
        document.write(year + " is a leap year." + "</br>");
    }
    else
    {
        document.write(year +" is not a leap year." + "</br>");
    }
}
//调用函数
isLeapYear(2000);
isLeapYear(2001);
isLeapYear(2020);

function getMax(a,b,c,d)
{
    var maxNum;
    maxNum = (a > b) ? a : b;
    maxNum = (maxNum > c) ? maxNum : c;
    maxNum = (maxNum > d) ? maxNum : d;
    return maxNum;
}
document.write("4个数中的最大值为：" + getMax(4,1,12,30));