jQuery scrollTop - Issue with wrong hash

Question

I am trying to do scrollTop animation to an anchor that resides inside of a fullscreen <section>, but does not scroll to right anchor at first click. Here's my code.

<nav id="scroller"> <a href="#subBox1">Scroll me to sub 1</a>
 <a href="#subBox2">Scroll me to sub 2</a>
 <a href="#subBox3">Scroll me to sub 3</a>

</nav>
<section id="boxTop"></section>
<section id="boxMaster">
    <section id="subBox1">
        <p>Hello. I am the Sub 1!</p>
    </section>
    <section id="subBox2">
        <p>Hello. I am the Sub 2!</p>
    </section>
    <section id="subBox3">
        <p>Hello. I am the Sub 3!</p>
    </section>
</section>

---

$("#scroller a").click(function () {
    $('#boxMaster').animate({
        scrollTop: $(this.hash).offset().top
    }, 700);
    $("#scroller a").removeClass("active");
    $(this).addClass("active");
});

fiddle

$("#scroller a").click(function() {
  $('#boxMaster').animate({
    scrollTop: $(this.hash).offset().top
  }, 700);
  $("#scroller a").removeClass("active");
  $(this).addClass("active");
});

html,
body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
}
#scroller {
  position: fixed;
  top: 0;
  height: 30px;
  text-align: center;
}
#scroller a {
  color: #fff;
  margin: 0 20px;
  text-decoration: none;
}
#scroller a.active {
  font-weight: bold;
  text-decoration: underline;
}
#boxTop {
  width: 100%;
  height: 100%;
  background: red;
}
#boxMaster {
  width: 100%;
  height: 100%;
  background: blue;
  overflow: hidden;
}
#boxMaster #subBox1,
#boxMaster #subBox2,
#boxMaster #subBox3 {
  width: 100%;
  height: 100%;
  display: table;
}
p {
  color: #fff;
  text-align: center;
  display: table-cell;
  vertical-align: middle;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<nav id="scroller"> <a href="#subBox1">Scroll me to sub 1</a>
  <a href="#subBox2">Scroll me to sub 2</a>
  <a href="#subBox3">Scroll me to sub 3</a>

</nav>
<section id="boxTop"></section>
<section id="boxMaster">
  <section id="subBox1">
    <p>Hello. I am the Sub 1!</p>
  </section>
  <section id="subBox2">
    <p>Hello. I am the Sub 2!</p>
  </section>
  <section id="subBox3">
    <p>Hello. I am the Sub 3!</p>
  </section>
</section>

Answer 1

I have a fixed header. I started with w3school's code. However, I've been struggling with this same problem for so long, finally found a workaround for the "first click incorrect" issue:

Just before (outside) of my click event, I simply created a variable "x", initialized:

var x=1;

Then I have a conditional statement inside the click event checking for x:

    if (x==1) {
        console.log("x is now: " + x);
        x=0;
        console.log("x is now: " + x);
        jQuery("html, body").animate({ 
            scrollTop: jQuery("div.class-of-element-i-am-scrolling-to" + hash).position().top - jQuery("div.header-container").outerHeight(true) - jQuery("h3.another-element-in-my-way").outerHeight(true)
            }, 2000, function(){
            return false;
        });
    } else {
        jQuery("html, body").animate({ 
            scrollTop: jQuery("div.class-of-element-i-am-scrolling-to" + hash).position().top
            }, 2000, function(){
            return false;
        });
    }

In other words, using "x" as a flag to check if it is the first time the code is run.

If it is, then I am kind of cheating by subtracting the fixed header and the other elements that are pulling my desired div up. Remember to make "x=0" to "drop" the flag.

If it isn't, then it works fine anyway.

Answer 2

You need to scroll the #boxMaster element relative to the link's position within the element and relative to the #boxMaster element's top position within the body element.

You can do this by adding the #boxMaster element's scrollTop() value with its top position, and then subtracting that from the link's offset top value:

$(this.hash).offset().top - $('#boxMaster').position().top + $('#boxMaster').scrollTop()

Updated Example

var $boxMaster = $('#boxMaster');
$boxMaster.animate({
    scrollTop: $(this.hash).offset().top - $boxMaster.position().top + $boxMaster.scrollTop()
}, 700);

You may also need to prevent the link element's default behavior using e.preventDefault(), and then manually scroll the html/body element to the #boxMaster element:

Updated Example

$('html, body').animate({
    scrollTop: $boxMaster.offset().top
}, 700);

Answer 3

Add the current scroller value to the offset().top(), the latter beeing relative to the top of frame, and get rid of this.hash. Use this.href instead.

$("#scroller a").click(function () {
    var y=$('#boxMaster').scrollTop()
    $('#boxMaster').animate({
        scrollTop: $(this.href).offset().top + y
    }, 100);
});