Introduction

ScrollShow is a JavaScript library to make DOM elements "scroll to show".

For example, if we want DOM elements to stay hidden initially and only becomes visible when user scrolls them into viewport.

Demo

Installation

Add the following script into the HTML file

<script src="https://cdn.jsdelivr.net/gh/iamfranco/scrollShow@v1.0.0/scrollShow.js"></script>

Usage

Step 1: CSS

Add a CSS rule for .scrollShow so that those elements are initially hidden.

Add a CSS rule for .scrollShow.show so that those elements can be visible later.

.scrollShow {
    opacity: 0; /* hidden */
    transition: 0.2s ease all;
}

.scrollShow.show {
    opacity: 1; /* now visible */
}

Step 2: HTML

For DOM elements that you want to "scroll to show", add a scrollShow class to them

<div class="[some class...] scrollShow">
    [some content ...]
</div>

Step 3: JavaScript

After the closing body tag, add the JavaScript

scrollShow.addItems()

so that all those DOM elements with the scrollShow class are tracked.

Step 4: And that's it

Now, whenever a tracked element gets scrolled "into view", the element will have the show class automatically added to it, which makes the element visible.

Advanced

HTML

There are more data- options that you can specify in an element for more fine tuned scrollShow behaviour

<div class="scrollShow" 
    data-scroll-show-class="show"
    data-scroll-show-element-percent="100"
    data-scroll-show-viewport-percent="0">
    [...]
</div>

data-scroll-show-class is the class name to be added to the element when it is "in view".
By default, that's the show class.
data-scroll-show-element-percent is how much an element (measuring from the top, in percentage of height) should be visible, in order for it to be considered "in view".
By default, that's 100%, i.e. right at the bottom of the element.
data-scroll-show-viewport-percent is where the "in view threshold" is located at within the viewport (measuring from the bottom, in percentage of height).
By default, that's 0%, i.e. right at the bottom of the viewport.

JavaScript

There are some properties within the scrollShow object that controls how scrollShow behaves

scrollShow.delay =  0.05 // time delay (seconds)
scrollShow.default_element_percent = 100 // percent of element height
scrollShow.default_viewport_percent = 0 // percent of viewport height
scrollShow.hide_on_scroll_back = false // hide elements when we scroll back?

.delay is the time (in seconds) it takes between consecutive elements become visible, so that they can appear "sequentially" as opposite to "suddenly all appearing at the same time".
.default_element_percent is the default value for the data-scroll-show-element-percent attribute.
.default_viewport_percent is the default value for the data-scroll-show-viewport-percent attribute.
.hide_on_scroll_back is boolean for if we want elements to hide when we scroll back up.