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!"; returnfalse; } } document.getElementById("notification").innerHTML = ""; document.getElementById("submit").removeAttribute("disabled"); // so that it allows form submission again; } CopySolution 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.<selectname="hssub1"id="hssub1"><optionvalue=null>Select</option> //added default option <optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectname="hssub2"id="hssub2"><optionvalue=null>Select</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectname="hssub3"id="hssub3"><optionvalue=null>Select</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectname="hssub4"id="hssub4"><optionvalue=null>Select</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectname="hssub5"id="hssub5"><optionvalue=null>Select</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectname="hssub6"id="hssub6"><optionvalue=null>Select</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><divid="notification"></div><buttontype="button"name="submit"id="submit">Save and Next</button>CopyHere's the Javascript -fairly straightforward, but you can ask in case of any questions:var selects = document.querySelectorAll('select'), notify = document.getElementById('notification'); functiongetOthers(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; } functioncheckUnique(){ 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 timeif(values.length < 6){ notify.innerText = 'select all six'; returnfalse; } notify.innerText = ''; returntrue; } CopyA 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> Copythen 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 nulldocument.getElementById("notification").innerHTML = "Select in all lists to continue"; // if null print this }elseif(othercodes[i] == hssubcode){ document.getElementById("submit").setAttribute("disabled","disabled"); document.getElementById("notification").innerHTML = elt.options[elt.selectedIndex].text + " Subject Already Choosen!"; returnfalse; break; } else{ document.getElementById("notification").innerHTML = ""; document.getElementById("submit").removeAttribute("disabled"); } } } Copybut with this at first time you enter the page the button will not disable. So for that call this function on body onload event;<bodyonload="checkUnique('hssub1');">CopyI think this will help you to continue with minimal changes to your existing codeSolution 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.jsYou need to give a class for all the < select > tags you want to have unique values Here I'm using class='abc' as example.<selectclass='abc'name="hssub1"id="hssub1"onchange="checkUnique(this.id);"><optionvalue="null">Select One</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select><selectclass='abc'name="hssub2"id="hssub2"onchange="checkUnique(this.id);"><optionvalue="null">Select One</option><optionvalue="1">Bengali</option><optionvalue="2">English</option><optionvalue="3">Hindi</option><optionvalue="4">Physics</option><optionvalue="5">Chemistry</option><optionvalue="6">Mathematics</option></select> and so on ..... CopyAnd call the constructor of Unique on window.onload like thisvar k = new Unique('.abc','null');//u need to have a default null valueCopyAnd 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:functioncheckUnique(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'); } } } CopyInstead 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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