JavaScript: Count and display the items of a dropdown list, in an alert window

Last update on May 30 2022 10:02:48 (UTC/GMT +8 hours)

JavaScript DOM: Exercise-9 with Solution

Write a JavaScript program to count and display the items of a dropdown list, in an alert window.

Sample Solution:-

HTML Code:

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Volume of a Sphere</title>
<style>  
body{padding-top:30px;}
label,input{display:block;}  
</style>
</head>
<body>
<p>Input radius value and get the volume of a sphere.</p>
<form action="" method="post" id="MyForm">
<label for="radius">Radius</label><input type="text" name="radius" id="radius" required>
<label for="volume">Volume</label><input type="text" name="volume" id="volume">
<input type="submit" value="Calculate" id="submit">    </form>
</body>
</html>

JavaScript Code:

function getOptions()
{
var x=document.getElementById("mySelect");
var txt1 = "No. of items : ";
var i;
l=document.getElementById("mySelect").length;  
txt1 = txt1+l;
for (i=0;i<x.length;i++)
  {
    txt1 = txt1 + "\n" + x.options[i].text;
  }
alert(txt1);
}

Sample Output:

Flowchart:

Live Demo:

See the Pen javascript-dom-exercise-9 by w3resource (@w3resource) on CodePen.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = []; arr[0] = "Jani"; arr[1] = "Hege"; arr[2] = "Stale"; arr[3] = "Kai Jim"; arr[4] = "Borge"; console.log(arr.join()); arr.splice(2, 0, "Lene"); console.log(arr.join());

Ref: https://bit.ly/2BXbp04