//是否判断
var flag = false;
if(flag){

    alert("flag为true");

}else{

    alert("flag为false");
};



//多条件判断
var day = 3;
if(day == 1){
    alert("day是1");

}else if(day == 2){
    alert("day是2");
}else if(day == 3){
    alert("day是3");
}else{
    alert("day是大于3");
};





//嵌套判断
var f = true;
var h = 200;
if(f){
    if(h > 100){

        alert("h大于100");
    }else{

        alert("h小于100");
    }


}else{
    alert("false");
};