CODEWITHSUNDEEP
jqueryvariablesscroll
user4991434
user4991434

Reputation:

Why must I use variable instead of just "0"?

When I change variable to 0, it doesn't work. Why must I use variable instead of just "0"?

Use 0 number instead of variable name and you will see. fiddle

$(function() {

  var zero = 0;
  $(window).scroll(function() {
    var top = $(this).scrollTop();
    if (top > zero) {
      $("nav").hide();
    } else if (top < zero) {
      $("nav").show();
    }
    zero = top;
  });

});
body {
  height: 1000px;
}

nav {
  width: 100%;
  height: 75px;
  background: #333;
  position: fixed;
  top: 0;
  left: 0;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<nav></nav>

Upvotes: 0

Views: 26

Answers (1)

David
David

Reputation: 218960

Why i must use variable instead of just "0"?

Because you're modifying the value. Here's what your code would look like if you tried to use a literal value instead of a variable:

$(window).scroll(function() {
  var top = $(this).scrollTop();
  if (top > 0) {
    $("nav").hide();
  } else if (top < 0) {
    $("nav").show();
  }
  0 = top; // <-- here is the problem
});

Clearly, that last line doesn't make sense. You can't modify a literal value. Storing a value and modifying it over time is exactly what a variable is for. So in this case you need to use a variable.

Upvotes: 1

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