JavaScript/addition-program-with-validation.html at master · eliCoding/JavaScript · GitHub

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<!DOCTYPE html>

<htmllang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<metacharset="utf-8" />
<title></title>
<scripttype="text/javascript">
/*prompt the user to enter 2 numbers and then display te sum*/

//1.Declaration Phase
varfirstNumber;// first number entered by user as a string
varsecondNumber;//second number entered bu used as a strng
varnumber1;//converted first number
varnumber2;//converted second number
varsum;//sum of number 1 and number 2
// 2. Initialization Phase
//read first number from a user as a String

//ensure that the value is numerical
while(isNaN(firstNumber=window.prompt("Please Enter First Number","0"))){
window.prompt("You have enterted"+firstNumber+".Please enter a number");

}//end while loop
while(isNaN(secondNumber=window.prompt("Please Enter Second Number","0"))){
window.prompt("You have enterted"+secondNumber+".Please enter a number");

}//end while loop
sum=0;

//3. Processing Phase
firstNumber=window.prompt("Enter first number");
number1=parseFloat(firstNumber);
secondNumber=window.prompt("Enter second number");
number2=parseFloat(secondNumber);
//add number one and number 2 to sum
sum=number1+number2;


//4. Termination Phase
document.writeln("<h2> the sum of "+firstNumber+" + "+secondNumber+" + "+sum.toPrecision(2)+"</h2>");


</script>
</head>
<body>

</body>
</html>