How to pass string value to javascript alert

Question

How do I pass string value to alert message for each empty field?

I have w, t, a, c and s. For example, if w is empty, it should give the alert message "Mandatory field w must be filled out". And same goes for others.

My javascript:

function addvalidation(){
        var w = document.forms["shop"]["w"].value;
        var t = document.forms["shop"]["t"].value;
        var a = document.forms["shop"]["a"].value;
        var c = document.forms["shop"]["c"].value;
        var s = document.forms["shop"]["s"].value;
        var c = document.forms["shop"]["c"].value;

        if (w == "" || t =="" || a == ""|| c == "" || s == "" || c == "") {
                alert("Mandatory fields must be filled out");
                return false;
            }

Better you have to keep if condition for all individual fields — Surendheran
– Surendheran, Commented May 14, 2015 at 9:29

A.B · Accepted Answer · 2015-05-14 09:59:17Z

You can filter where document.forms["shop"][e].value=="" and join them for displaying in alert

Note/update: You need to join keys not value

e = Object.keys(document.forms["shop"]).filter(function(e){
            return document.forms["shop"][e].value==""
        });


   errors = e.join(" ");
   alert(errors +" are mandatory");

Working Demo:

        document.forms["shop"] =[] ;

        document.forms["shop"]["w"] = {};
        document.forms["shop"]["t"]={};
        document.forms["shop"]["a"] ={};
        document.forms["shop"]["c"]= {};

        
        document.forms["shop"]["w"].value = "";
        document.forms["shop"]["t"].value="abc";
        document.forms["shop"]["a"].value = "";
         document.forms["shop"]["c"].value="abcd";
        

    e = Object.keys(document.forms["shop"]).filter(function(e){
        return document.forms["shop"][e].value==""
    });
   
   
   errors = e.join(" ");
   alert(errors +" are mandatory");

Arun P Johny · Accepted Answer · 2015-05-14 09:35:21Z

2

You can try something like

function addvalidation() {
  var form = document.forms["workshop"];
  var ef = ['w', 't', 'a', 'c', 's'].filter(function(f) {
    return !form[f].value
  })

  if (ef.length) {
    alert("Mandatory fields " + ef.join() + " must be filled out");
    return false;
  }
}

<form name="workshop" onsubmit="return addvalidation()">
  <input name="w" />
  <input name="t" />
  <input name="a" />
  <input name="c" />
  <input name="s" />
  <input type="submit" />
</form>

edited May 14, 2015 at 9:35

answered May 14, 2015 at 9:29

Arun P Johny

389k68 gold badges532 silver badges532 bronze badges

6 Comments

Cloudburst Over a year ago

Wow thank you so much! But sorry, how do you make a field not mandatory but once entered must follow the email format. For example, email in this case is not compulsory and can be left empty, but when user type inside it must follow email format. jsfiddle.net/Qc2bd/577

Cloudburst Over a year ago

Need your most valuable help again. When i try to include the codes in this format. The filter doesn't work. jsfiddle.net/tn2fvh4p/68

Arun P Johny Over a year ago

@Cloudburst that is a server side template.... what is the generated html.... in the browser select view source and check the generated html

Arun P Johny Over a year ago

@Cloudburst what is the server side technology used

Arun P Johny Over a year ago

@Cloudburst it can't be because there is no tag called form:input... are you using any html namespacing....

|

Surendheran · Accepted Answer · 2015-05-14 09:50:33Z

0

Try this for specific field alert,

function addvalidation() {
   var form = document.forms["workshop"];
   var field="";
   var ef = ['w', 't', 'a', 'c', 's'].filter(function(f) {
     if(form[f].value=="" && field==""){
        field=f; 
     }
   })

  if (field!="") {
    alert("Mandatory field " + field + " must be filled out");
    return false;
  }
}

answered May 14, 2015 at 9:50

Surendheran

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