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Exercise 1.1 - Buttons and Inputs

f) Validate input

This is the console. All output created with writeLog() is shown here.

Please type the radius of a circle and press "Calculate". I will print the areas and circumference for the circle to the console. This time, I will also check your inputs.

script.js

This is the JavaScript code behind the above application.

/* global writeLog, getInput */
writeLog("Solution for exercise 1.1 f)");
function calculate() {
 // Get the radius from the user
 var radius = getInput("radius");
// Make it a number
 radius = parseFloat(radius);
// Check whether the parsing was successful
 if (isNaN(radius)) {
 writeLog("Ooops, the radius must be a number! This isn't a number: " + getInput("radius"));
 } else if (radius <= 0) {
 writeLog("Ooops, the radius must be a greater than 0!");
 } else {
writeLog("You entered the following radius: " + radius);
var area = calculateArea(radius);
 var circumference = calculateCircumference(radius);
writeLog("The area is: " + area.toFixed(2));
 writeLog("The circumference is: " + circumference.toFixed(2));
 }
// Clear the input field
 document.getElementById("radius").value = "";
}
// A function to calculate the area
function calculateArea(radius) {
 return Math.PI * radius * radius;
}
// A function to calculate the circumference
function calculateCircumference(radius) {
 return 2 * Math.PI * radius;
}