scroll-into-view

This modifier scrolls to the associated element. By default it uses scrollIntoView, but if a top or left offset is passed as an option it uses scrollTo and calculates the options.top and/or options.left attribute.

When you should use this modifier

You should use this modifier whenever you need to have an element scrolled into view. If there is a element, such as a fixed header or sidebar, passing in a topOffset or leftOffset will scroll to the element minus the that offset value.

Basic Usage

scroll-into-view expects the named shouldScroll parameter and an optional options named parameter. See scrollIntoView for the list of possible values and properties of options.

  <div {{scroll-into-view shouldScroll=this.shouldScroll options=(hash behavior="smooth")}}>
    <button type="button" {{on "click" this.onScrollIntoView}}>
      Trigger scroll-into-view on click
    </button>
  </div>

shouldScroll can be either a Boolean or a Promise that resolves to a truthy or falsy value. It does not handle a rejected Promise.

Usage with offset

When passing in an offset, it will call scrollTo, and the options parameter is designed to correspond to its options. The options.behavior operates the same, however, instead of top and left there are topOffset and leftOffset, respectively. As with top and left, topOffset and leftOffset are in pixels. If an offset value is not set then the value passed to scrollTo is 0, e.g. options = { topOffset: 10 } results in element.scrollTo({ top: [computedValue], left: 0 }). Experiment with the below example, you may need to zoom and resize the window to see a horizontal scrollbar.

  <div {{scroll-into-view shouldScroll=this.shouldScrollWithOffset options=(hash topOffset=this.topOffset leftOffset=this.leftOffset behavior="smooth")}}>
    <div>
      <label for="topOffset">Top Offset: </label>
      <input name="topOffset" type="number" value={{this.topOffset}} {{on "change" this.onTopOffsetChange}}>
    </div>
    <div>
      <label for="leftOffset">Left Offset: </label>
      <input name="leftOffset" type="number" value={{this.leftOffset}} {{on "change" this.onLeftOffsetChange}}>
    </div>
    <button type="button" {{on "click" this.onScrollIntoViewWithOffset}}>
      Trigger scroll-into-view with offset on click
    </button>
  </div>

shouldScroll can be either a Boolean or a Promise that resolves to a truthy or falsy value. It does not handle a rejected Promise.

A custom scroll container id can be passed. This allows scrolling in nested scroll containers with an offset instead of the main window.

  <div>
    <label for="topOffset">Top Offset: </label>
    <input name="topOffset" type="number" value={{this.topOffsetCustom}} {{on "change" this.onTopOffsetChangeCustom}}>
  </div>
  <div id="custom-scroll-container" style="width: 200px; height: 150px; overflow-y: scroll;">
    <div style="background-color: red; height: 100px;">Item 1</div>
    <div style="background-color: green; height: 100px;">Item 2</div>
    <div
      style="background-color: blue; height: 100px;"
      {{scroll-into-view shouldScroll=this.shouldScrollWithCustom options=(hash topOffset=this.topOffsetCustom scrollContainerId='custom-scroll-container')}}
    >
      Item 3
    </div>
    <div style="background-color: yellow; height: 100px;">Item 4</div>
    <div style="height: 100px;">Item 5</div>
  </div>
  <button type="button" {{on "click" this.onScrollIntoViewWithCustom}}>
    Trigger scroll-into-view with offset on click
  </button>

Testing

scroll-into-view-mock provides a function that will mock the native browser scrollIntoView and allow testing which elements invoked the modifier

mockScrollIntoView() - will mock the native API and return an object with the following 2 functions

• scrollIntoViewCalledWith(Element|DOM selector) - tests if the modifier was invoked on the element
• resetMock() - restores the native scrollIntoView function

import mockScrollIntoView from 'ember-scroll-modifiers/test-support/scroll-into-view-mock';
...
hooks.beforeEach(function () {
  this.mockHelperFunctions = mockScrollIntoView();
});

hooks.afterEach(function () {
  this.mockHelperFunctions.resetMock();
});
...
function('test scroll into view', (assert) => {
  ...
  await render(
    hbs`<div {{scroll-into-view shouldScroll=true}} data-test-scroll-into-view-selector></div>`
  );
  ...
  assert.ok(this.mockHelperFunctions.scrollIntoViewCalledWith('[data-test-scroll-into-view-selector]'), 'element scrolled into view');
});

function('test scroll into view with offset', (assert) => {
  ...
  await render(
    hbs`<div {{scroll-into-view shouldScroll=true options=(hash offset=25)}} data-test-scroll-into-view-selector></div>`
  );
  ...
  assert.ok(this.mockHelperFunctions.scrollIntoViewCalledWith('[data-test-scroll-into-view-selector]', { behavior: 'smooth', top: 25, left: 0 }), 'scrolled to element');
});

Browser Support

This feature is supported in the latest versions of every browser. This feature is supported in the latest versions of every browser.