SOURCE

var a = 1;


if (a == 1)
{
    document.write("单向"+"</br>");
}


if (a == 2)
{
    document.write("a");
}
else
{
    document.write("双向"+"</br>");
}


if(a==2)
{
    document.write("a");
}
else if(a==3)
{
    document.write("b");
}
else
{
    document.write("多向"+"</br>");
}


if (a == 2)
{
    if (a == 2)
    {
        document.write("a");
    }
    else
    {
        document.write("b");
    }
}
else
{
    if (a == 1)
    {
        document.write("嵌套"+"</br>");
    }
    else
    {
        document.write("b");
    }
}

function isI(num)
{
    var res = false;
    if(parseInt(num)==num) 
    {
        res = true;
    }
    return res;
}

function isF(num)
{
    var res = false;
    if(parseInt(num)!=num) 
    {
        res = true;
    }
    return res;
}

if(isI(15))
{
    document.write("15 is an integer"+"<br/>");
}

if(isF(15.15))
{
    document.write("15 is an float"+"<br/>");
}