Javascript – How to determine the direction of a jQuery scroll event

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I'm looking for something to this effect:

$(window).scroll(function(event){
   if (/* magic code*/ ){
       // upscroll code
   } else {
      // downscroll code
   }
});

Any ideas?

Best Answer

Check current scrollTop vs previous scrollTop

var lastScrollTop = 0;
$(window).scroll(function(event){
   var st = $(this).scrollTop();
   if (st > lastScrollTop){
       // downscroll code
   } else {
      // upscroll code
   }
   lastScrollTop = st;
});

Related Solutions

Javascript – How to check if an element is hidden in jQuery

Since the question refers to a single element, this code might be more suitable:

// Checks CSS content for display:[none|block], ignores visibility:[true|false]
$(element).is(":visible");

// The same works with hidden
$(element).is(":hidden");

It is the same as twernt's suggestion, but applied to a single element; and it matches the algorithm recommended in the jQuery FAQ.

We use jQuery's is() to check the selected element with another element, selector or any jQuery object. This method traverses along the DOM elements to find a match, which satisfies the passed parameter. It will return true if there is a match, otherwise return false.

Javascript – How to insert an item into an array at a specific index (JavaScript)

You want the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert).

In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join()); // Jani,Hege,Stale,Kai Jim,Borge
arr.splice(2, 0, "Lene");
console.log(arr.join()); // Jani,Hege,Lene,Stale,Kai Jim,Borge

Best Answer

Related Solutions

Javascript – How to check if an element is hidden in jQuery

Javascript – How to insert an item into an array at a specific index (JavaScript)

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