Math.trunc()
BaselineWidely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
TheMath.trunc() static method returns the integer part of a number by removing any fractional digits.
Try it
console.log(Math.trunc(13.37));// Expected output: 13console.log(Math.trunc(42.84));// Expected output: 42console.log(Math.trunc(0.123));// Expected output: 0console.log(Math.trunc(-0.123));// Expected output: -0Syntax
Math.trunc(x)Parameters
xA number.
Return value
The integer part ofx.
Description
The wayMath.trunc() works is more straightforward than the other threeMath methods:Math.floor(),Math.ceil() andMath.round(); ittruncates (cuts off) the dot and the digits to the right of it, no matter whether the argument is a positive or negative number.
Becausetrunc() is a static method ofMath, you always use it asMath.trunc(), rather than as a method of aMath object you created (Math is not a constructor).
Examples
Using Math.trunc()
Math.trunc(-Infinity); // -InfinityMath.trunc("-1.123"); // -1Math.trunc(-0.123); // -0Math.trunc(-0); // -0Math.trunc(0); // 0Math.trunc(0.123); // 0Math.trunc(13.37); // 13Math.trunc(42.84); // 42Math.trunc(Infinity); // InfinityUsing bitwise no-ops to truncate numbers
Warning:This is not a polyfill forMath.trunc() because of non-negligible edge cases.
Bitwise operations convert their operands to 32-bit integers, which people have historically taken advantage of to truncate float-point numbers. Common techniques include:
const original = 3.14;const truncated1 = ~~original; // Double negationconst truncated2 = original & -1; // Bitwise AND with -1const truncated3 = original | 0; // Bitwise OR with 0const truncated4 = original ^ 0; // Bitwise XOR with 0const truncated5 = original >> 0; // Bitwise shifting by 0Beware that this is essentiallytoInt32, which is not the same asMath.trunc. When the value does not satisfy -231 - 1 <value < 231 (-2147483649 <value < 2147483648), the conversion would overflow.
const a = ~~2147483648; // -2147483648const b = ~~-2147483649; // 2147483647const c = ~~4294967296; // 0Only use~~ as a substitution forMath.trunc() when you are confident that the range of input falls within the range of 32-bit integers.
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-math.trunc |