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/>"); 



//<a href="javascript:welcomeMes">Welcome</a> 

//add(1, 2) + 3 ;

//定义函数
function addSum(a, b) 
{
     var sum = a + b;
    return sum;
}
    //调用函数
    var n = addSum(1, 2) + 100;
    document.write(n+ "<br/>");

//function expressMes() 
    //{ alert("她：我爱helicopter。\n我：oh~my，= =?!"); } 
//< a href=" ">表白对话</ a> 


function isLeapYear(year) 

{
    if(year % 4 == 0 )
    {
        document.write(year +' is a Leap Year'+ "<br/>"); 
    }
    else
    {
        document.write(year +' is  not a Leap Year'+ "<br/>"); 

    }

}

isLeapYear(2020); 
isLeapYear(2000); 
isLeapYear(2001); 

writeDocument("//---比较大小------------------------------------------------------------------");
//求出4个数中的最大值
//很简单，定义一个变量，然后每次比较两个数后，较大的数赋值给变量就可以了。
var sy=[23,179,3,78];
function comparer(a)
{
    var max=0;
    for(var i=0;i<a.length;i++)
    {
        if(a[i]>=max)
        {
            max=a[i];
        }

    }
    return max;
}
writeDocument(comparer(sy)+ "<br/>");


writeDocument("//---定义两个函数，它们的功能分别是求出任意五个数中最大最小-------");

function max(sy)
{
    var temp=sy[0];
    for (var i=0;i<sy.length;i++)
    {
        if(temp<=sy[i])
        {
            temp=sy[i];
        }
    }
    return temp;

}


function min(sy)
{
    var temp=sy[0];
    for (var i=0;i<sy.length;i++)
    {
        if(temp>=sy[i])
        {
            temp=sy[i];
        }
    }
    return temp;

}
b=[23,234,8,221,76];
document.write(max(b)+ "<br/>");
document.write(min(b)+ "<br/>");


var welcomeString="Welcome";

document.write(welcomeString.length+ "<br/>");

function writeDocument(variable)
{
    document.write(variable + "<br/>");
} 

var welcomeString="Welcome";

writeDocument(welcomeString);
writeDocument(welcomeString.length);

writeDocument("//---case------------------------------------------------------------------");
writeDocument(welcomeString.toLocaleLowerCase);
writeDocument(welcomeString.toLocaleUpperCase);

writeDocument("//---chatAt------------------------------------------------------------------");
writeDocument(welcomeString.charAt(2));
writeDocument(welcomeString.charAt(6));

writeDocument("//---substring------------------------------------------------------------------");
writeDocument(welcomeString.substring(3));
writeDocument(welcomeString.substring(0,2));

var sentence="We have fun in our class.Do you have fun in your class?"

writeDocument(sentence);
writeDocument(sentence.replace("class","programming class"));
writeDocument(sentence.replace(/class/g,"programming class"));

writeDocument("//---split------------------------------------------------------------------");
writeDocument(sentence.split(" "));
writeDocument(sentence.split(""));
writeDocument(sentence.split("."));

writeDocument("//---indexOf/lastIndexOf/match/search------------------------------------------------------------------");
writeDocument(sentence.indexOf("class"));
writeDocument(sentence.lastIndexOf("class"));
writeDocument(sentence.match("class"));
writeDocument(sentence.match(/class/g));
writeDocument(sentence.search(/class/g));


function countChar(stringToCount, char)
{
    var charCount = 0;
    for (var i=0;i<stringToCount.length;i++)
    {

        if (stringToCount.charAt(i).toLowerCase()==char)
        {
            charCount++;
        }

    }

    return charCount;
}
var stringToCount = "Can you can a can as a Canner  a can I u";
writeDocument("There are " + countChar(stringToCount, "c") + " c in " + stringToCount); 
writeDocument("There are " + countChar(stringToCount, "n") + " n in " + stringToCount); 





function countNumber(stringtoCount)
{

    var numCount = 0;

     //实现你的逻辑
    for (var i=0;i<stringtoCount.length;i++)
    {
        if (stringtoCount.charAt(i)!=" "&&!isNaN(stringtoCount.charAt(i)))
        {
            numCount++;
        }

    }

     return numCount;

}

var stringtoCount = "172 Yuzuru Haruv1994";
writeDocument("There are " + countNumber(stringtoCount) + " number in " + stringtoCount); 

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        function welcomeMes()
        {
            alert("生命不息，\n代码不止！");
        }
    </script>
</head>
<body>
    < a href=" ">Welcome</ a> 
</body>
</html>