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Replace text with empty string by class in html using javascript

I'm trying to create a js function which removes text onclick from a certain class of fields in HTML.
When checking Yes in the trigger (onclick), the function is not clearing the data in my target.
This works if I substitute id for class where appropriate, but I need the function to affect 10+ html fields. Can this be accomplished by class?
Note: There is a little extra in the HTML below because there is another js function run onclick in my trigger. I've removed the divs, so it's less cluttered.
JavaScript
function eraseText() {
document.getElementsByClassName("eraseonupdate").value = "";
}
HTML
Trigger:
<input type="radio" name="exceptionupdate" class="_exceptionupdate" value="Yes" onclick="ExceptionUpdate();eraseText()" />Yes <input type="radio" name="exceptionupdate" class="_exceptionupdate" value="No" onclick="ExceptionUpdate()" />No
Target:
<input type="text" name="Approver" size="20" class="eraseonupdate">

That's because the two methods return different values.
getElementById will return one HTML object (as an id should be unique).
getElementsByClassName will return a HTMLCollection (as classes do not need to be unique). To alter the value of each of the items in this collection, you need to loop over them.
For example
var elements = document.getElementsByClassName("eraseonupdate");
for (var i = 0; i < elements.length; i++) {
elements[i].value = ""
}

You need to iterate the result of .getElementsByClassName(), to make that easier you can convert it to an array, like so:
function eraseText() {
var elements = document.getElementsByClassName('eraseonupdate');
Array.prototype.slice.call(elements).forEach(function(el) {
el.value = '';
});
// if you do not need old browsers to work you could do
/*
[...elements].forEach(el => {
el.value = '';
});
*/
}
function ExceptionUpdate() {
return;
}
<input type="text" name="Approver" size="20" class="eraseonupdate">
<label><input type="radio" name="exceptionupdate" class="_exceptionupdate" value="Yes" onclick="ExceptionUpdate();eraseText()" />Yes</label>
<label><input type="radio" name="exceptionupdate" class="_exceptionupdate" value="No" onclick="ExceptionUpdate()" />No</label>

Call to getElementsByClassName("class") returns a collection of elements. Iterate over them and clear value in a loop. Use value or other attribute or innerHTML depending on your need:
function clearText() {
var elements = document.getElementsByClassName("abc");
[...elements].forEach(element => {
element.value = "";
// element.innerHTML="";
});
}
Instead of [...elements].forEach() you may use Array.from(elements).forEach().

Selecting all textbox at once with javascript

In my work we have to fill a lot of textboxes to do some validations. After all, we need to erase all - one by one - to restart the process.
Has some way to erase all textbox content with javascript (the only one method we can use now)? A for loop maybe?

You should put all the input fields in a form and then reset the form by the .reset() method.
document.getElementById("reset").onclick= ()=>{
document.getElementById("form").reset()
}
<form id="form">
<input/>
<input/>
</form>
<button id="reset">Reset</button>
See an example on W3Schools or the docs on MDN

If you want to restore the fields to their initial value, reset the form as suggested by #dota2pro's answer.
OTOH, if you want to clear the elements regardless of their initial value, you can query the elements using a type (aka "tag") CSS selector via Document​.query​SelectorAll()
and iterate through the elements as below:
function go() {
let inputs = document.querySelectorAll('input');
for (var i = 0; i < inputs.length; i++) {
inputs[i].value = '';
}
}
<input type="text" value="a"><br>
<input type="text" value="b"><br>
<input type="text" value="c"><br>
<br>
<button onclick="go()">click to clear</button>
Note that:
document.querySelectorAll('input') fetches all <input>s regardless of their type attribute.
document.querySelectorAll('input[type="text"]') fetches all <input type="text">.
document.querySelectorAll('textarea') fetches all <textarea>.
If you want to combine, you can use the comma combinator:
document.querySelectorAll('input[type="text"],textarea')

You can get in different ways in javascript:
By ID : document.getElementById("id")
By class: document.getElementsByClassName("class")
By tag:
document.querySelectorAll("input")
or Jquery
By ID : $("#id")
By class: $(".class")
By tag: $("input")
Read documentation about that here

tru
[...document.querySelectorAll('input')].map(x=>x.value='')
var clean = () => [...document.querySelectorAll('input')].map(x=>x.value='');
<button onclick="clean()">Clear</button><br>
<input type="text" value="some"><br>
<input type="text" value="short"><br>
<input type="text" value="text"><br>

Bellow code will select all editable text-boxes
document.querySelectorAll('input[type="text"]:not(:disabled):not([readonly]))')

If you have JQuery available, you can do:
$('input[type="text"]').val('');
Or, if you prefer native:
for(var i = 0; i < document.getElementsByTagName('input').length; i++){
document.getElementsByTagName('input')[i].value = '';
}

Javascript set value for Form obeject Array

I am looking to add data to a form object which is an array.
This works fine:
<input type="text" name="object" value="">
<script>document.form.object.value = "value";</script>
But when the object is an array it's not working:
<input type="text" name="object[]" value="">
<script>document.form.object[0].value = "value";</script>
The value of the object is not changing.... Any idea?
I would like to loop the script so I need to create an array. Didn't find any solution...

Per example, I would utilize document.form.elements['object[]'].value = "value". Otherwise, if you intended on having multiple form elements with the same name (multiple inputs with object[], and iterate via the collection, can use the following:
var myForm = document.form;
var myControls = myForm.elements['object[]'];
for (var i = 0; i < myControls.length; i++) {
var aControl = myControls[i];
}
The example provided, in your code, the name provided is not perceived as an array.

The attribute value "object[]" is just a string to JavaScript -- it does not interpret that as an array. However, when brackets appear in a name, you cannot use it any more in the dot-notation, but must write:
document.form["object[]"].value = "value";
<form name="form">
<input type="text" name="object[]" value="">
</form>
If you have more than one element with name="object[]", then the above will only target the first one of these. To set the value of all those elements, you must loop. This you can (for instance) do with the elements property and Array.from to iterate over those elements:
Array.from(document.form.elements["object[]"], function(elem) {
elem.value = "value";
});
<form name="form">
<input type="text" name="object[]" value="">
<input type="text" name="object[]" value="">
</form>
For those using IE: replace Array.from with [].map.call

how to get input array value by key with javascript function?

Here is sample code i try to create input array with key and on change i want to get the value of individual input array value.
<input type="text" name="items[1]" value="443" onchange="get_items(1)">
<input type="text" name="items[2]" value="233" onchange="get_items(2)">
<script>
function get_items(key)
{
alert($("items["+key+"]").val());
}
</script>

Simply pass this context as argument and get value.
<input type="text" name="items[1]" value="443" onchange="get_items(this)">
<input type="text" name="items[2]" value="233" onchange="get_items(this)">
<script>
function get_items(ele) {
alert(ele.value);
}
</script>

Refer fiddle
HTML:
<input type="text" name="items[1]" value="443" onchange="get_items(1)">
<input type="text" name="items[2]" value="233" onchange="get_items(2)">
JS:
function get_items(key)
{
alert($('input[name="items['+key+']"]').val());
}

You can get the event's target from event,
function get_items(e) {
console.log(e.target.value);
}
<input type="text" name="items[1]" value="443" onchange="get_items(event)">
<input type="text" name="items[2]" value="233" onchange="get_items(event)">
or, better, attach your listener in javascript:
function get_items(e) {
console.log(e.target.value);
};
var inputs = document.querySelectorAll("input");
for (var i = 0, el; i < inputs.length; i += 1) {
el = inputs[i]
el.addEventListener("change", get_items);
};
<input type="text" name="items[1]" value="443">
<input type="text" name="items[2]" value="233">

Here is some code that does what (I think) you are trying to do:
<input type="text" name="item1" value="443" onchange="javascript:get_items(1)">
<input type="text" name="item2" value="233" onchange="javascript:get_items(2)">
<script>
function get_items(key)
{
//alert($("items["+key+"]").val());
var input = $('input[name="item' + key + '"]');
var value = input.val();
alert(value);
}
</script>
jsfiddle: https://jsfiddle.net/9kvv2q7p/4/

You can use this
function get_items(key) {
alert($("input[name='items[" + key + "]']").val());
}
I hope I was helpfull

Your HTML is missing a closing quote for the name attributes.
The name attribute should not contain [ or ]
characters. Adding these characters will complicate matters.
You should hook up your event handlers in JavaScript, not HTML.
When practical, elements should have unique id attributes added to them, which will make accessing and identifying them much easier in JavaScript and CSS
Rather than trying to identify the textboxes with indexes, just gather them up and place them into an array or array-like container, where indexes will be automatically assigned to them.
Here is a working example of how to get values by index:
// This will scan the DOM and place all matched elements into a node list
// which is an array-like object
var textBoxes = document.querySelectorAll("input[type=text]");
// Or, you can get references to them individually:
var txt1 = document.getElementById("txt1");
var txt2 = document.getElementById("txt2");
// And, put them into an array on your own:
var ary = [txt1, txt2];
// No matter how you got your references to them, it's best to hook
// them up to event handler in JavaScript, not HTML
txt1.addEventListener("change", get_items2);
txt2.addEventListener("change", get_items2);
function get_items(key) {
// You can certainly pass a key to this function
// to identify which element you are talking about
alert(textBoxes[key].value);
}
function get_items2(evt) {
// But, event handlers are automatically passed
// a reference to the object that fired the event
alert(evt.target.value);
}
get_items(0); // Call the function to get first textbox value
get_items(1); // Call the function to get second textbox value
<input type="text" id="txt1" name="txt1" value="443">
<input type="text" id="txt2" name="txt2" value="233">

Clone form and increment ID

Consider the following form:
<form>
<input type="button" value="Input Button"/>
<input type="checkbox" />
<input type="file" id="file"/>
<input type="hidden" id="hidden"/>
<input type="image" id="image" />
<input type="password" id="password" />
<input type="radio" id="radio" />
<input type="reset" id="reset" />
</form>
Utilizing Javascript (and jQuery), what would be the easiest way to clone the entire form and increment each individual id within, to ensure uniqueness.
Using jQuery I would assume you would clone the form initially via clone() and iterate through the cloned objects id and add the new id fieldname1, fieldname2 etc. However, my knowledge of jQuery isn't too great and this project is almost killing me.
Any help would be great!

You would clone() it, and before attaching the cloned element to the DOM, you'd run through and add the number to each id attribute.
(function() {
var count = 0;
window.duplicateForm = function()
var source = $('form:first'),
clone = source.clone();
clone.find(':input').attr('id', function(i, val) {
return val + count;
});
clone.appendTo('body');
count++;
};
})();
jsFiddle.
This one starts with 0, but you could easily start count with 1.
You could also use a closure if you wanted, i.e.
var cloneForm = function(form, start) {
start = start || 0;
return function() {
var clone = form.clone();
clone.find(':input').attr('id', function(i, val) {
return val + start;
});
start++;
return clone;
};
};
Then you would do...
var cloneContactForm = cloneForm($('#contact-form'), 5);
// Now I want to clone it and put it somewhere.
$(cloneContactForm()).appendTo('body');
jsFiddle.

Here's a solution without updating any ids:
Give all forms the same class
Give all fields a name
Refer to cloned forms relative to all the forms with the class
Refer to fields with their name
Example:
How about giving each cloned form a different id, and then using names for each input element?
<form class="theForm">
<input type="password" name="password" />
</form>
Then Clone it with
container.append($('.theForm:first').clone());
(or cache the first form in a variable).
Finally, access the input fields with:
$('form.theForm:eq(0) [name=password]') // password from first form
$('form.theForm:eq(1) [name=password]') // password from second form
...
If the selector lookup efficiency is a factor here then there are several trivial ways to speed it up, such as caching variables with the different forms, caching $('.theForm') and using the eq() method, etc.
Sample jsFiddle is here: http://jsfiddle.net/orip/dX4sY