Chapter 23: Output Element

Attribute	Description
Global	Attributes that are available to any HTML5 element. For comprehensive documentation of these attributes see: MDN Global attributes
name	A string representing the name of an output. As a form element, output can be referenced by it’s name using the document.forms property. This attribute is also used for collecting values on a form submit.
for	A space separated list of form element ids (e.g. <inputs id=“inp1”> for value is “inp1”) that the output is meant to display calculations for.
form	A string representing the <form> that is associated to the output. If the output is actually outside the , <form> this attribute will ensure that the output still belongs to the <form> and subject to collections and submits of said <form>.

Output Element Using For and Form Attributes

The following demo features an <output> element’s use of the [for] and [form] attributes. Keep in mind, <output> needs JavaScript in order to function. Inline JavaScript is commonly used in forms as this example demonstrates. Although the <input> elements are type=”number”, their values are not numbers, they are text. So if you require the values to be calculated, you must convert each value into a number using methods such as: parseInt(), parseFloat(), Number(), etc.

Live demo

<!--form1 will collect the values of in1 and in2 on 'input' event.-->
 <!--out1 value will be the sum of in1 and in2 values.--> 
<form id="form1" name="form1" oninput="out1.value = parseInt(in1.value, 10) + parseInt(in2.value,
10)">
 <fieldset>
 <legend>Output Example</legend>
 <input type="number" id="in1" name="in1" value="0">
 <br/>
 +
 <input type="number" id="in2" name="in2" value="0">
 </fieldset>
</form>
<!--[for] attribute enables out1 to display calculations for in1 and in2.-->
<!--[form] attribute designates form1 as the form owner of out1 even if it isn't a descendant.-->
<output name="out1" for="in1 in2" form="form1">0</output>

Output Element with Attributes

<output name="out1" form="form1" for="inp1 inp2"></output>