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JavaScript

Posted by Mohamed Saied
Mohamed Saied
Courses Plus Student 293 Points

JavaScript Random numbers generator

in the "JavaScript Full-Stack developer" in "Random Numbers" lessons. we use Math.Floor to generate Integers , but why we don't use Math.round ? like this, Math.round(Math.random() * 6)

and a second question :

can we use this code : var input = parseInt( prompt("your age") )

instead of this : var input = prompt("your age"); var topNumber = parseInt(input);

???

1 Answer

Samuel Ferree
Samuel Ferree
31,723 Points

Math.round would generate a set of numbers that doesn't falls within your expected range, and it wouldn't be statistically accurate. Goal Table:

Value Probability
0 1/6
1 1/6
2 1/6
3 1/6
4 1/6
5 1/6

vs what you would get with math.round

Value Probability
0 1/12
1 1/6
2 1/6
3 1/6
4 1/6
5 1/6
6 1/12

Per your second question, you could use that line of code, but you would lose the user input, would could be useful if they made a mistake, like so:

var input = prompt("your age");
var topNumber = parseInt(input);
if(topNumber === NaN) {
  alert("Sorry " + input + " is not a number");
}