How To Synchronize Two Select Elements

I was wondering how to synchronize the values and text of two elements. For instance, OneSolution 1: One possible approach:functionsync(el1, el2) { // if there is no el1 argument we quit here:if (!el1) { returnfalse; } else { // caching the value of el1:var val = el1.value; // caching a reference to the element with// with which we should be synchronising values:var syncWith = document.getElementById(el2); // caching the <option> elements of that <select>:var options = syncWith.getElementsByTagName('option'); // iterating over those <option> elements:for (var i = 0, len = options.length; i < len; i++) { // if the value of the current <option> is equal// to the value of the changed <select> element's// selected value:if (options[i].value == val) { // we set the current <option> as// as selected: options[i].selected = true; } } } } // caching the <select> element whose change event should// be reacted-to:var selectToSync = document.getElementById('box1'); // binding the onchange event using an anonymous function: selectToSync.onchange = function(){ // calling the function:sync(this,'box2'); }; Copyfunctionsync(el1, el2) { if (!el1) { returnfalse; } else { var val = el1.value; var syncWith = document.getElementById(el2); var options = syncWith.getElementsByTagName('option'); for (var i = 0, len = options.length; i < len; i++) { if (options[i].value == val) { options[i].selected = true; } } } } var selectToSync = document.getElementById('box1'); selectToSync.onchange = function() { sync(this, 'box2'); };Copy<selectid="box1"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><selectid="box2"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>CopyJS Fiddle demo.Or, revised and updated somewhat:functionsync() { // caching the changed element:let el = this; // retrieving the id of the element we should synchronise with// from the changed-element's data-syncwith custom attribute,// using document.getElementById() to retrieve that that element.document.getElementById( el.dataset.syncwith ) // retrieving the <options of that element// and finding the <option> at the same index// as changed-element's selectedIndex (the index// of the selected <option> amongst the options// collection) and setting that <option> element's// selected property to true: .options[ el.selectedIndex ].selected = true; } // retrieving the element whose changes should be// synchronised with another element:var selectToSync = document.getElementById('box1'); // binding the snyc() function as the change event-handler: selectToSync.addEventListener('change', sync); Copyfunctionsync() { let el = this; document.getElementById(el.dataset.syncwith).options[el.selectedIndex].selected = true; } var selectToSync = document.getElementById('box1'); selectToSync.addEventListener('change', sync);Copy<selectid="box1"data-syncwith="box2"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><selectid="box2"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>CopyJS Fiddle demo.Note that this approach does assume – and requires – that the <option> elements are in the same order.To update the original approach, where the order is irrelevant, using ES6 approaches (and the same data-syncwith custom attribute approach):functionsync() { // caching the changed element (since// we're using it twice):let el = this; // retrieving the id of the element to synchronise 'to' from // the 'data-syncwith' custom attribute of the changed element,// and retrieving its <option> elements. Converting that// Array-like collection into an Array using Array.from():Array.from(document.getElementById(el.dataset.syncwith).options) // Iterating over the array of options using// Array.prototype.forEach(), and using an Arrow function to// pass the current <otpion> (as 'opt') setting that current// <option> element's selected property according to Boolean// returned by assessing whether the current option's value// is (exactly) equal to the value of the changed element: .forEach(opt => opt.selected = opt.value === el.value); } var selectToSync = document.getElementById('box1'); selectToSync.addEventListener('change', sync); Copyfunctionsync() { let el = this; Array.from(document.getElementById(el.dataset.syncwith).options).forEach(opt => opt.selected = opt.value === el.value); } let selectToSync = document.getElementById('box1'); selectToSync.addEventListener('change', sync);Copy<selectid="box1"data-syncwith="box2"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><selectid="box2"><optionvalue="1">One</option><optionvalue="3">Three</option><optionvalue="2">Two</option></select>CopyJS Fiddle demo.If you look at the HTML in the Snippet you'll see that I switched the positions of <option> elements in the second <select> element to demonstrate that the <option> position doesn't matter in this latter approach.References:Array.from().Array.prototype.forEach().Arrow functions.document.getElementById().EventTarget.addEventListener().for loop.HTMLElement.dataset.HTMLSelectElement.let statement.var.Solution 2: In the Actual browsers you dont have to do to much...<selectid="box1"onchange="box2.value=this.value;"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><selectid="box2"><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>CopyJsfiddle DEMOSolution 3: Without jQuery: for (var i=0; i<document.getElementById('box1').options.length; i++) if (document.getElementById('box1').options[i].selected) for (var j=0; j<document.getElementById('box2').options.length; j++) if (document.getElementById('box1').options[i].value == document.getElementById('box2').options[j].value) document.getElementById('box2').options[j].selected = true; CopySolution 4: With jQuery:Note:on method requires jQuery > 1.7jQuery(function($) { $('#first').on('change', function() { var sel = $('option:selected', this).val(); $('#second option').filter(function(index, el) { return el.value == sel; }).prop('selected', true); }); });Copy<selectname="first"id="first"autocomplete="off"><optionvalue="0">-- Select one option --</option><optionvalue="1">First</option><optionvalue="2">Second</option><optionvalue="3">Third</option><optionvalue="4">Fourth</option><optionvalue="5">Fifth</option><optionvalue="6">Sixth</option></select><selectname="second"id="second"autocomplete="off"><optionvalue="0">-- Select one option --</option><optionvalue="1">First</option><optionvalue="2">Second</option><optionvalue="3">Third</option><optionvalue="4">Fourth</option><optionvalue="5">Fifth</option><optionvalue="6">Sixth</option></select><scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>Copy Share Post a Comment for "How To Synchronize Two Select Elements" Top Question How Do You Make An Html Page Fade Out While Another Fades In? 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