Please explain

Question

Can someone please explain. See code below. When removing the parseInt on line two the code still works. However, without the parseInt it dosen't round the number to a whole input by the user. For example user = 3.3 return = 3 (parseInt).

What i would like to know, can someone please give me a simple example to where I would need the parseInt in real life. Does it matter that I have or have not used parseInt in this code and what scenario where it would matter if I did not use the parseInt. Hope I'm making sense.

var input = prompt("Plese type a number");
var topNumber = parseInt(input);
var randomNumber = Math.floor(Math.random() * topNumber) + 1;
var message = "<p>" + randomNumber + " is a number between 1 and " + topNumber + ".</P>";
document.write(message);

Answer 1 · 2017-10-12T17:16:53Z

October 12, 2017 5:16pm

The parseInt function converts the input from a string into a number. It doesn't actually "round" but it ignores anything that is not a digit (and what follows).

If you leave it out, then when you multiply by topNumber, the system performs "type coercion" for you, converting the string into a number (but not forcing it to be "int").

But using the parseInt, your program is in control of when, and how, the conversion happens.

Answer 2 · 2017-10-12T16:51:10Z

October 12, 2017 4:51pm

Hi Desmond,

Say you have 2 numbers that come from user input as strings. If you tried to add these two strings together you would end up concatenating them. If you parse these values as integers they will be mathematically added.

A simple example:

let number1 = "10"; //user input
let number2 = "4"; // user input

console.log(number1+number2); // 104
console.log(parseInt(number1)+parseInt(number2)); // 14

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Desmond Dallas

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Please explain

2 Answers

Steven Parker

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Desmond Dallas

Desmond Dallas

Tom Gooding

Tom Gooding

Steven Parker

Steven Parker