math-expm1.js 450 Bytes
var nativeExpm1 = Math.expm1;
var exp = Math.exp;

// `Math.expm1` method implementation
// https://tc39.github.io/ecma262/#sec-math.expm1
module.exports = (!nativeExpm1
  // Old FF bug
  || nativeExpm1(10) > 22025.465794806719 || nativeExpm1(10) < 22025.4657948067165168
  // Tor Browser bug
  || nativeExpm1(-2e-17) != -2e-17
) ? function expm1(x) {
  return (x = +x) == 0 ? x : x > -1e-6 && x < 1e-6 ? x + x * x / 2 : exp(x) - 1;
} : nativeExpm1;