Prompt command syntax

Question

Im currently reading eloquent JavaScript and this was an example for using the prompt command:

var theNumber = Number(prompt("Pick a number", " "));

Why does the bolded need to be there? Is that the way of letting the computer know what kind of entry was entered? If it was a set of words would it be String(prompt("Pick a number", " "));

Welcome to the documentation on Number.

tadman
– tadman

2017-08-24 18:02:33 +00:00
Commented Aug 24, 2017 at 18:02 — tadman
– tadman, Commented Aug 24, 2017 at 18:02

abagshaw · Accepted Answer · 2017-08-24 18:08:21Z

1

If you just used:

var theNumber = prompt("Pick a number");

The variable theNumber would be set to a string. For example if the user entered 5, then theNumber would equal "5". Number() is a function in javascript that will convert a string to a number, meaning if you use:

var theNumber = Number(prompt("Pick a number"));

Then theNumber would equal 5 or whatever the user entered.

If you wanted to convert a number back into a string, you would use:

var stringOfTheNumber = theNumber.ToString();

edited Aug 24, 2017 at 18:08

abagshaw

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answered Aug 24, 2017 at 18:05

Will Hamic

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2 Comments

tadman Over a year ago

Also worth mentioning that Number() is considered harmful. Number("0x100") returns 256. Instead use Number.parseInt(..., 10) where in that case you'll get 0.

Will Hamic Over a year ago

Also it is important to use try, catch statements in the event that the user doesn't enter a number.

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