The <output> tag is used to display the result of the calculation. The content is written between the start and end tag of <output> tag. The HTML5 specification defines it as “result of calculation or an action”. If you look at the below example, this <output> tag simplifies the calculation of two fields by just taking the values and parsing it to the output field without any major extra work for the programmer.
Syntax of <output> tag
[code lang=”html”]
<output name= ""> Text</output>
[/code]
Supported Browsers
<output> tag in HTML5 is supported in Firefox, Opera, Chrome, and Safari.
Attributes of <output> Tag
Along with the global attribute the following attribute are supported by <output> tag.
- name: This attribute specifies the name of the tag.
- form: This attribute specifies the output of an tag that it belongs. The value must be the ID of a form in the same document.
- for: This attribute specifies the relationship between the result of calculation and the tags that represents the values of the calculation.
Output Tag Example
[code lang=”html”]
<!DOCTYPE html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<h4>Example of output tag using <i>name</i> attriute</h4>
<form oninput="o.value = parseInt(a.value) + parseInt(b.value)">
<input name="a" type="number"> +
<input name="b" type="number"> =
<output name="o"></output>
</form>
<h4>Example of output tag using <i>name</i> and <i>for</i> attriutes</h4>
<form oninput="o.value = parseInt(a.value) + parseInt(b.value)">
<input name="a" type="number"> +
<input name="b" type="number"> =
<output name="o" for="a b"></output>
</form>
</body>
</html>
[/code]
- <form oninput= form oninput=”o.value = parseInt(a.value) + parseInt(b.value)”> tag is used to specify output of an tag that it belongs. The value must be the ID of a form in the same document
Example Application Test
- Save the file as output_example.html in your system.
- Just open the file in the browser, you will see the below picture in the browser. Note that the browser must support HTML5 specification.
Output
When the execution process is completed successfully we will get the following output :
Enter some numbers and you would see the result as shown below:
You can notice that if you enter only a single value, the function returns NaN. It’s effectively trying to add a number and an undefined value, and 1 + undefined = undefined as shown below:
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