Question

56

How to force JS to do math instead of putting two strings together

rated 0 times [ 57] [ 1] / answers: 1 / hits: 142531 / 14 Years ago, sun, january 30, 2011, 12:00:00

I need javascript to add 5 to an integer variable, but instead it treats the variable as a string, so it write out the variable, then add 5 onto the end of the string. How can I force it to do math instead?

var dots = document.getElementById(txt).value; // 5

function increase(){

    dots = dots + 5;

}

Output: 55

How can I force it to output 10?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

dakotahs

Add To Favorites

Follow

Total Points: 605

Total Questions: 104

Total Answers: 113

Location: Hungary

Member since Wed, Nov 9, 2022

2 Years ago

answered 14 Years ago jaylynbrynnk · Accepted Answer

You have the line

dots = document.getElementById(txt).value;

in your file, this will set dots to be a string because the contents of txt is not restricted to a number.

to convert it to an int change the line to:

dots = parseInt(document.getElementById(txt).value, 10);

Note: The 10 here specifies decimal (base-10). Without this some browsers may not interpret the string correctly. See MDN: parseInt.