Number Truncation in JavaScript
Published in
3 min readApr 8, 2019
Use Math.trunc()
to truncate a floating point number and return its integer part. This function doesn't do any rounding, it simply removes all the digits following the decimal. Now you have a whole number, yay 🎊
const number = 80.6// Old Way
number < 0 ? Math.ceil(number) : Math.floor(number);
// 80// ✅ES6 Way
const es6 = Math.trunc(number);
// 80
Example
Math.trunc()
simply truncates (cuts off) the dots and the digits to the right of it. No matter whether the argument is a positive or negative number.
Math.trunc(80.9); // 80
Math.trunc(80.8); // 80
Math.trunc(80.8); // 80
Math.trunc(80.6); // 80
Math.trunc(80.5); // 80
Math.trunc(80.4); // 80
Math.trunc(80.3); // 80
Math.trunc(80.2); // 80
Math.trunc(80.1); // 80Math.trunc(-80.1); // -80
Now let’s see some examples with non-number arguments:
Math.trunc('80.1'); // 80
Math.trunc('hello'); // NaN
Math.trunc(NaN); // NaN
Math.trunc(undefined); // NaN
Math.trunc(); // NaN
Number truncation using parseInt
You can get a similar result using parseInt
parseInt(80.1); // 80
parseInt(-80.1); // -80