vanillafocus VS shariff

/** * vanillafocus; version: 1.0.0 * Author: https://simon-koehler.com/en * Source: https://github.com/koehlersimon/vanillafocus * Copyright (c) 2020 S.Köhler; MIT License */ ( function( root, factory ) { var pln = 'vanillafocus'; if (typeof define === 'function' && define.amd) { define([],factory(pln)); } else if (typeof exports === 'object' ) { module.exports = factory(pln); } else { root[pln] = factory(pln); } }( this, function(pln) { 'use strict'; var defaults = { reCalcOnWindowResize: true, throttleDuration: 17 }; /** * @param {Object} defaults * @param {Object} options */ var extend = function( target, options ) { var prop, extended = {}; for ( prop in defaults ) { if ( Object.prototype.hasOwnProperty.call( defaults, prop ) ) { extended[ prop ] = defaults[ prop ]; } } for ( prop in options ) { if ( Object.prototype.hasOwnProperty.call( options, prop ) ) { extended[ prop ] = options[ prop ]; } } return extended; }; /** * @param {Object} options * @constructor */ function Plugin( options ) { this.options = extend( defaults, options ); this.init(); } /** * @public * @constructor */ Plugin.prototype = { init: function() { var selectors = document.querySelectorAll( this.options.selector ); selectors.forEach((el, i) => { var fp = focusPoint(el,this.options); if (this.options.reCalcOnWindowResize) fp.windowOn(); }); }, adjustFocus: function() { var selectors = document.querySelectorAll( this.options.selector ); selectors.forEach((el, i) => { adjustFocus(el); }); } }; var setupContainer = function(focusElement) { let imageSrc = focusElement.querySelector('img').getAttribute('src'); focusElement.setAttribute('data-image-src', imageSrc); resolveImageSize(imageSrc, function(err, dim) { focusElement.setAttribute('data-image-w', dim.width); focusElement.setAttribute('data-image-h', dim.height); adjustFocus(focusElement); }); }; var resolveImageSize = function(src, cb) { let image = document.createElement('img'); image.src = src; image.addEventListener('load',function(e){ cb(null, { width: e.target.width, height: e.target.height }); }); }; var throttle = function(fn, ms) { var isRunning = false; return function() { var args = Array.prototype.slice.call(arguments, 0); if (isRunning) return false; isRunning = true; setTimeout(function() { isRunning = false; fn.apply(null, args); }, ms); }; }; var calcShift = function(conToImageRatio, size, imageSize, focusSize, toMinus) { var center = Math.floor(size / 2); var focusFactor = (focusSize + 1) / 2; var scaledImage = Math.floor(imageSize / conToImageRatio); var focus = Math.floor(focusFactor * scaledImage); if (toMinus) focus = scaledImage - focus; var focusOffset = focus - center; var remainder = scaledImage - focus; var containerRemainder = size - center; if (remainder < containerRemainder) focusOffset -= containerRemainder - remainder; if (focusOffset < 0) focusOffset = 0; return (focusOffset * -100 / size) + '%'; }; var adjustFocus = function(focusElement) { var imageW = focusElement.getAttribute('data-image-w'); var imageH = focusElement.getAttribute('data-image-h'); var imageSrc = focusElement.getAttribute('data-image-src'); if (!imageW || !imageH || !imageSrc) { return setupContainer(focusElement); } var containerW = focusElement.offsetWidth; var containerH = focusElement.offsetHeight; var focusX = parseFloat(focusElement.getAttribute('data-focus-x')); var focusY = parseFloat(focusElement.getAttribute('data-focus-y')); var image = focusElement.querySelector('img'); var hShift = 0; var vShift = 0; if (!(containerW > 0 && containerH > 0 && imageW > 0 && imageH > 0)) { return false; } var wR = imageW / containerW; var hR = imageH / containerH; image.style.maxWidth = ''; image.style.maxHeight = ''; if (imageW > containerW && imageH > containerH) { if((wR > hR)){ image.style.maxHeight = '100%'; } else{ image.style.maxWidth = '100%'; } } if (wR > hR) { hShift = calcShift(hR, containerW, imageW, focusX); } else if (wR < hR) { vShift = calcShift(wR, containerH, imageH, focusY, true); } image.style.top = vShift; image.style.left = hShift; }; var focusPoint = function(el, options) { var thrAdjustFocus = options.throttleDuration ? throttle(function(){adjustFocus(el);}, options.throttleDuration) : function(){adjustFocus(el);}; var isListening = false; adjustFocus(el); return { adjustFocus: function() { return adjustFocus(el); }, windowOn: function() { if (isListening) return; window.addEventListener('resize',thrAdjustFocus); return isListening = true; }, windowOff: function() { if (!isListening) return; window.removeEventListener('resize',thrAdjustFocus); isListening = false; return true; } }; }; return Plugin; } ) );

One implementation, pioneered by a German tech magazine: https://github.com/heiseonline/shariff