function isToday(str){
    var d = new Date(str.replace(/-/g,"/"));
    var todaysDate = new Date();
    if(d.setHours(0,0,0,0) == todaysDate.setHours(0,0,0,0)){
        return true;
    } else {
        return false;
    }
}

console.log(isToday('2018-01-22'));  //这里的01也可以直接是1
console.log(isToday('2014-07-08'));