Posted By
Bajarangi soft ,
Posted On 25-09-2020
Function Parameters and Arguments
Earlier in this tutorial, you learned that functions can have parameters:
function functionName(parameter1, parameter2, parameter3) {
// code to be executed
}
Function parameters are the names listed in the function definition.
Function arguments are the real values passed to (and received by) the function.
JavaScript function definitions do not specify data types for parameters.
JavaScript functions do not perform type checking on the passed arguments.
JavaScript functions do not check the number of arguments received.
Parameter Defaults
If a function is called with missing arguments (less than declared), the missing values are set to: undefined
Sometimes this is acceptable, but sometimes it is better to assign a default value to the parameter:
Example(1)
<script>
function multiplication(x, y) {
if (y === undefined) {
y = 0;
}
return x * y;
}
document.getElementById("demo").innerHTML = myFunction(4);
</script>
The Arguments Object
JavaScript functions have a built-in object called the arguments object.
The argument object contains an array of the arguments used when the function was called (invoked).
This way you can simply use a function to find (for instance) the highest value in a list of numbers:
Example(2)
<script>
function findMax() {
var i;
var max = -Infinity;
for(i = 0; i < arguments.length; i++) {
if (arguments[i] > max) {
max = arguments[i];
}
}
return max;
}
document.getElementById("demo").innerHTML = findMax(4, 5, 10,45);
</script>
Example(3)
Create a function to sum all input values:
<script>
function sum() {
var i;
var sum = 0;
for(i = 0; i < arguments.length; i++) {
sum += arguments[i];
}
return sum;
}
document.getElementById("demo").innerHTML = sum(1, 123, 500, 115, 44, 88);
</script>
Arguments are Passed by Value
The parameters, in a function call, are the function's arguments.
JavaScript arguments are passed by value: The function only gets to know the values, not the argument's locations.
If a function changes an argument's value, it does not change the parameter's original value.
Changes to arguments are not visible (reflected) outside the function.
Complete code for function parameter in java script
<!DOCTYPE html>
<html>
<head>
<title>Function Parameters In JavaScript</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css">
</head>
<style>
h2{
color:red;
}
</style>
<body>
<div class="container">
<div class="text-center">
<h1>Function Parameters In JavaScript</h1>
</div>
<div class="well">
<h2>Finding Maximum Value</h2>
<h1 id="demo1"></h1>
<h2>Finding Sum of Numbers</h2>
<h1 id="demo2"></h1>
</div>
<br>
</div>
</body>
</html>
<script>
function findMax() {
var i;
var max = -Infinity;
for(i = 0; i < arguments.length; i++) {
if (arguments[i] > max) {
max = arguments[i];
}
}
return max;
}
document.getElementById("demo1").innerHTML = findMax(4, 5, 10,45);
function sum() {
var i;
var sum = 0;
for(i = 0; i < arguments.length; i++) {
sum += arguments[i];
}
return sum;
}
document.getElementById("demo2").innerHTML = sum(1, 123, 500, 115, 44, 88);
</script>