How to increment a value in Javascript with a value the user defines

Question

I want to write a loop that will display numbers from 1-100 in multiples that the user picks.

Here's my JS code.

 var x = prompt("Enter the increment you want to see")

   for (i=0;i<=100;i=i+x) {
    document.write(i+"</br>")
   }

For example, if I enter "10" I want the code to print the numbers 10, 20,30,40,50,60,70,80,90,100

Why does this not work?

I am teaching myself Javascript, and I am going crazy trying to figure this out.

Can anyone help?

eladcon · Accepted Answer · 2015-03-17 18:47:13Z

3

The returned value from prompt is string. You need to parse it as a number (with the radix value as stated in the comments):

var x = parseInt(prompt("Enter the increment you want to see"), 10);

answered Mar 17, 2015 at 18:40

eladcon

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2 Comments

Worth noting that it's still recommended to use the radix parameter when using parseInt, at least for the time being.

Thank you so much! I'll never forget that prompt returns a string value.

Aswin Ramakrishnan · Accepted Answer · 2015-03-17 18:41:32Z

1

You need to parse x. The following code should work -

var x = parseInt(prompt("Enter the increment you want to see"));

for (i = 0; i <= 100; i = i + x) {
  document.write(i + " </br>");
}

answered Mar 17, 2015 at 18:41

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Probably more efficient to parse it once at the beginning instead of each iteration of the loop.