how to call javascript function in html & JavaScript Define

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In how to call javascript function in html, JavaScript is a programming language commonly used in single page web applicaiton to perform some js methods or pure js based functions that the HTML DOM cannot do. It can be help for get a really and tru data for validating forms, and accessing your browsers data, including the dynamic any run time Implements statement, module and more!

What is Function in JavaScript?

In example how to call javascript function in html, JS Functions are Main imp part as well as helfup in any devlop programming language like as a js, php or any client side as they make the scripts reusable A User-defined function is a block of scripts which will be run ot executed only if it is called. If you have a some source code lines of scripts that requires to be used more times, you can make a User-defined function added the repeating some basic lines of scripts and then this js call the User-defined function wherever you want.

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How to Create a Function in JavaScript

  • Use the keyword function followed by the name of the User-defined function.
  • Now the User-defined function name, open as well as close parentheses.
  • Now parenthesis, open as well as close your function curly braces.
  • Within curly braces, write your lines of scripts.

Syntax:

function callJsUserFunc()
{

  lines of source scripts to be run or executed

}

Example

<html>
<head>
	<title>Functions!!! - call javascript function from html</title>
	<script type="text/javascript">
      function callJsUserFunc()
      {
      	document.write("This is a simple function.<br />");
      }
		callJsUserFunc();
	</script>
</head>
<body>
</body>
</html> 

Function with Arguments

You can make a simple JS functions with Parameters as well. Parameters should be specified within parenthesis

Read Also:  call javascript function from html

Syntax:

//call javascript function from html
function callJsUserFunc(param1, param2)
{

  lines of source scripts to be run or executed

}

Example: call javascript function from html

<html>
<head>
<title>call javascript function from html</title>
	<script type="text/javascript">
		var count = 0;
		function countVowels(user_info)
		{
			for (var i=0;i<user_info.length;i++)
			{
              if(user_info[i] == "a" || user_info[i] == "e" || user_info[i] == "i" || user_info[i] == "o" || user_info[i] == "u")
              count = count + 1;
			}
		document.write("Grettings " + user_info + "!!! Your user_info has " + count + " vowels.");
		}
   	 	var userInformation = prompt("Please enter your Good User Information");
    	countVowels(userInformation);
	</script>
</head>
<body>
</body>
</html> 

JavaScript Return Value

You can also make a JS functions that data return values. Inside the JavaScript User-defined function, you required to use the main keyword return bellow by the value to be returned.

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Syntax:

function callJsUserFunc(param1, param2)
{

  lines of source scripts to be run or executed

  return val1;

}

Example : call javascript function from html

<html>
<head>
	<script type="text/javascript">
		function totalCountOfData(beging, lastdata)
        {
          var total = beging + lastdata;
          return total;
        }
      var beginingPersonId = 89;
      var lastPersonId = 65;
      document.write(beginingPersonId + " + " + lastPersonId + " = " + totalCountOfData(beginingPersonId,lastPersonId));
	</script>
</head>
<body>
</body>
</html>

how to call javascript function in html?

It is beyond the scope of this guide to teach you JavaScript, but below you can learn how to embed or integrate JavaScripts into your website using the Download

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