How To Select Unique Values From Multiple Dropdown Lists Using JavaScript?

I am building an online registration form. In the web form, there are six dropdown lists which is as follows : ).value, document.getElementById('hssub2').value, document.getElementById('hssub3').value, document.getElementById('hssub4').value, document.getElementById('hssub5').value, document.getElementById('hssub6').value ]; for(var i=0; i<=5; i++){ var c = valCounter[othercodes[i]] = (valCounter[othercodes[i]] || 0) + 1; if(c > 1){ document.getElementById("submit").setAttribute("disabled","disabled"); // so that it stops form submission; document.getElementById("notification").innerHTML = elt.options[elt.selectedIndex].text + " Subject Already Choosen!"; return false; } } document.getElementById("notification").innerHTML = ""; document.getElementById("submit").removeAttribute("disabled"); // so that it allows form submission again; } Copy Solution 2: First, I would suggest using a default option like "Select subject" whose value is "null" or 0 - something that can be easily discarded. This way there are no default selected values. Second, I would highly recommend not putting the event handlers in your markup. It's a real mess to maintain that. <select name="hssub1" id="hssub1"> <option value=null>Select</option> //added default option <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select name="hssub2" id="hssub2"> <option value=null>Select</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select name="hssub3" id="hssub3"> <option value=null>Select</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select name="hssub4" id="hssub4"> <option value=null>Select</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select name="hssub5" id="hssub5"> <option value=null>Select</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select name="hssub6" id="hssub6"> <option value=null>Select</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <div id="notification"></div> <button type="button" name="submit" id="submit">Save and Next</button> Copy Here's the Javascript -fairly straightforward, but you can ask in case of any questions: var selects = document.querySelectorAll('select'), notify = document.getElementById('notification'); function getOthers(current){ var values = []; for(var i=0;i<selects.length;i++){ if(selects[i].value!='null' && selects[i]!=current) values.push(selects[i].value); } return values; } function checkUnique(){ if(this.value && getOthers(this).indexOf(this.value)>-1){ notify.innerText = 'You already selected that'; this.value = null; } } for(var i=0;i<selects.length;i++) selects[i].onchange = checkUnique; document.getElementById('submit').onclick = function(){ var values = getOthers(); // will return all selected values this time if(values.length < 6){ notify.innerText = 'select all six'; return false; } notify.innerText = ''; return true; } Copy A fiddle: http://jsfiddle.net/p699m9x7/ Solution 3: First add new option to lists with an value you can easily recognize like this: <select name="hssub1" id="hssub1" onchange="checkUnique(this.id);"> <option value="null">Select</option> <option value="1">Bengali</option> Copy then add if condition before the conditions you have now and then the loop will be like this: for(var i=0; i<=5; i++){ if(i != elementIDsuffix){ if(othercodes[i] === "null"){ //check whether anything is null document.getElementById("notification").innerHTML = "Select in all lists to continue"; // if null print this }else if(othercodes[i] == hssubcode){ document.getElementById("submit").setAttribute("disabled","disabled"); document.getElementById("notification").innerHTML = elt.options[elt.selectedIndex].text + " Subject Already Choosen!"; return false; break; } else{ document.getElementById("notification").innerHTML = ""; document.getElementById("submit").removeAttribute("disabled"); } } } Copy but with this at first time you enter the page the button will not disable. So for that call this function on body onload event; <body onload="checkUnique('hssub1');"> Copy I think this will help you to continue with minimal changes to your existing code Solution 4: There's this JavaScript snippet on github. Just a 1.4 kB js file. Just include jquery before including the script and you should be good to go. https://github.com/akhilnaik/unique.js You need to give a class for all the < select > tags you want to have unique values Here I'm using class='abc' as example. <select class='abc' name="hssub1" id="hssub1" onchange="checkUnique(this.id);"> <option value="null">Select One</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> <select class='abc' name="hssub2" id="hssub2" onchange="checkUnique(this.id);"> <option value="null">Select One</option> <option value="1">Bengali</option> <option value="2">English</option> <option value="3">Hindi</option> <option value="4">Physics</option> <option value="5">Chemistry</option> <option value="6">Mathematics</option> </select> and so on ..... Copy And call the constructor of Unique on window.onload like this var k = new Unique('.abc','null');//u need to have a default null value Copy And thats it everything is taken care of. The selected values will automatically be disabled. Dont forget to include JQuery before including unique.js Hope this helps. Solution 5: I don't know if this fits your needs, but if you want to get a warning, if any value is already chosen, you could do it like that: function checkUnique(elementID) { var values = []; var elements = document.getElementsByTagName('select'); for (var i=0, l=elements.length; i < l; i++) { if (document.getElementById(elementID).value === elements[i].value && document.getElementById(elementID) != elements[i]) { console.log('not unique'); } } } Copy Instead of console.log('not unique') you could do your warnings. Share Post a Comment for "How To Select Unique Values From Multiple Dropdown Lists Using JavaScript?" 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