Develop JavaScript to implement functions
Laboratory Objective:
- To be able to understand the concept of functions.
- To develop JavaScript to implement the given function.
- To develop JavaScript to calling function from HTML.
- To be develop JavaScript to returning a value from a function.
JavaScript Functions
- A function is block of code designed to perform a particular task.
- It is reusable code which can be called anywhere in program.
- There are two types of functions:
1) Built-in functions
2) User-defined functions
Defining a function
- A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().
- Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).
- The parentheses may include parameter names separated by commas: (parameter1, parameter2, …)
- It is recommended that the function should define in <head> tag.
- A function definition consists of four parts:
1) Function name
2) Parenthesis
3) Code block
4) Return statement (Optional) - Syntax:
function functionName([arg1, arg2, ...argN])
{
// code to be executed
return val;
}
- Example:
function cube(a)
{
document.write(a*a*a);
}
Function without arguments
<html>
<head>
<script>
function msg()
{
alert("Hi, Welcome to JavaScript");
}
</script>
</head>
<body>
<input type="button" onclick="msg()" value="Call Function"/>
</body>
</html>
Function with arguments
<html>
<head>
<script>
function cube(num)
{
alert(num*num*num);
}
</script>
</head>
<body>
<input type="button" onclick="cube(4)" value="Find Square"/>
</body>
</html>
Function with a return value
<html>
<head>
<script>
function getSquare(s)
{
return s * s;
}
document.write(getSquare(9));
</script>
</head>
<body>
</body>
</html>
Sample Programs
1) Develop a program to create a function sum which takes two parameters as number and display the addition numbers provided
<html>
<head>
<script>
function sum(val1, val2) {
var result = val1 + val2;
document.write(result + "<br/>");
}
</script>
</head>
<body>
<script>
sum(23, 19);
sum(32, 56);
sum(12, 52);
</script>
</body>
</html>
2) Develop a program to convert temperature from Celsius to Fahrenheit by returning value from function.
<html>
<head>
<script>
function toFahrenheit(celsius) {
return (celsius * 9/5 + 32);
}
document.write("Temperature in Fahrenheit is " +
toFahrenheit(45));
</script>
</head>
<body>
</body>
</html>
