check values of a form's fields with javascript

Question

i want to check if values of a form is empty or not? i am trying to write my own validator after many validators like jquery.ketchup.0.3.2 failed me (or maybe i failed them ) but i cant make this function to work.

function validate() {
    alert("hmmm");
    var inputs = document.forms["register"].getElementsByTagName("input");
    for (var item in inputs) {
        if(item.value.trim() == "")
            alert("nullField");
    }
}

would you please tell me what is wrong with the above function?

which error do you get? where are you applying this function in the HTML? Can you post a jsfiddle? — Saturnix
– Saturnix, Commented Apr 23, 2013 at 13:43

Ian · Accepted Answer · 2013-04-23 13:51:02Z

3

I'm wondering if it's the for loop you used. To loop over a collection (array), use a normal for loop, not a for in. Maybe this fixes it:

function validate() {
    alert("hmmm");
    var inputs = document.forms["register"].getElementsByTagName("input");
    for (var i = 0; i < inputs.length; i++) {
        if(inputs[i].value.trim() == "")
            alert("nullField");
    }
}

Note that .trim() isn't available in all browsers: http://kangax.github.io/es5-compat-table/#String.prototype.trim

A jQuery alternative, probably preferred, is to use something like:

$('form[name="register"]').find('input[type="text"]').each(function () {
    var $this = $(this);
    if (!$.trim($this.val())) {
        // Left empty
    }
});

References:

.find(): http://api.jquery.com/find/
.each(): http://api.jquery.com/each/
.trim(): http://api.jquery.com/jQuery.trim/

edited Apr 23, 2013 at 13:51

answered Apr 23, 2013 at 13:44

Ian

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2 Comments

MoienGK Over a year ago

thnx - it worked :) just for clarification can i change change other attributes of null fileds by calling inputs[i].someMethod on them?

Ian Over a year ago

@dave Yep, exactly. For example, you could change their border with inputs[i].style.border = "1px solid #ff0000";

ahren · Accepted Answer · 2013-04-23 13:50:26Z

3

If you're going to use jQuery, then use jQuery.

validate(){
  var $inputs = $('input', 'form[name="register"]');
  $inputs.each(function(){
    var val = $.trim(this.value);
    if(!val.length){
       // Not valid
    }
  });
}

edited Apr 23, 2013 at 13:50

answered Apr 23, 2013 at 13:44

ahren

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3 Comments

Ian Over a year ago

If you're going to suggest using jQuery, then use it to do everything the OP had. You left out the .forms["register"] part

ahren Over a year ago

@Ian - the OP suggested using jQuery when they tagged the question jQuery. Have updated with your point though, well caught.

Ian Over a year ago

My only point was that you didn't find the form first, that's it.

d3mi3n · Accepted Answer · 2013-04-23 14:10:13Z

0

If you want to use only javascript:

1st of all make sure that the trim function is defined:

if(!String.prototype.trim) {
  String.prototype.trim = function () {
    return this.replace(/^\s+|\s+$/g,'');
  };
}

Now for actual function:

 function validate() {
    var inputs = document.forms["register"].getElementsByTagName("input");
    for (var i = 0, len = inputs.length; i < len ; i++) {
        if(inputs[ i ].value.trim() == ""){
            // Validation failed
        }
    }
    // Validation successful
}

edited Apr 23, 2013 at 14:10

answered Apr 23, 2013 at 13:57

d3mi3n

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Comments

andresuribe · Accepted Answer · 2013-04-23 13:58:50Z

I strongly (and I mean STRONGLY) recommend not writing your own validations. Nevertheless, there are a couple of things that are wrong with your code.

The for..var..in construct iterates through all the properties of the object. So an object foo = { bar: '0', baz: '1'} would iterate through bar and baz (the properties, not the values). If you want to get the value you need to indicate so by doing for(var i in foo){ console.log(foo[i]);}, or in your example: inputs[item].value.
The getElementsByTagName return a NodeList (see here ). NodeLists have additional properties beside the elements in the list.

If you're using jQuery, then you simply do $("#register input").val() to get the array of relevant values and you can use the $.map function to do something for each value.

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