EmielZuurbier

/**
 * Returns an array of elements that are currently in view.
 * @param {string} selector A CSS selector to query elements.
 * @param {boolean} partially Detect elements that are partially in view. Otherwise they would have to be fully in view.
 * @returns {Promise<HTMLElement[]>}
 */
const getElementsInView = (selector = '*', partially = true) =>
  new Promise(resolve => {
    const elements = document.querySelectorAll(selector)

EmielZuurbier

/**
 * Checks if an image has a data-src or data-srcset attribute
 * and returns the answer in a Promise.
 * 
 * @param 		{HTMLImageElement} image The image to check
 * @returns		{boolean} True when data attributes are present, false when not.
 */
export const isImageLazyLoadable = image => 
	image.getAttribute('data-src') !== null || image.getAttribute('data-srcset' !== null);

EmielZuurbier

/**
 * Wrapper for creating a reusable template string based on a callback given
 * by the user. The template string will be wrapped in a <template> element to
 * clone the instance of the rendered template.
 */
class Template {

	/**
	 * Rendered string of template.
	 * 

EmielZuurbier

/**
 * Not precisely a "read-only" property but it can (in the near future) behave as one with 
 * ES2019 spec private instance fields. With a single get method and a "private instance field" 
 * it is possible to simulate the effect, like the examples above, with the added bonus of having 
 * the private property truly hidden.
 *
 * Although MDN is not the ultimate authority, their examples don't show the necessity to have a `setter`
 * with a `getter`. Making having only a `getter` already a case of having a "read-only" value. 
 *
 * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields