⚙ Compilation target
ES2017
⚙ Library
lib.es2015.core.d.ts
Missing / Incorrect Definition
It seems like "…of the a numeric expression…" might be a typo?
/**
* Returns the integral part of the a numeric expression, x, removing any fractional digits.
* If x is already an integer, the result is x.
* @param x A numeric expression.
*/
trunc(x: number): number;
Source: https://github.com/microsoft/TypeScript/blob/main/src/lib/es2015.core.d.ts#L175-L180
Sample Code
Documentation Link
MDN: Math.trunc()