shim.js #1

// Parts of implementation taken from es6-shim project
// See: https://github.com/paulmillr/es6-shim/blob/master/es6-shim.js

"use strict";

var expm1 = require("../expm1")
  , abs   = Math.abs
  , exp   = Math.exp
  , e     = Math.E;

module.exports = function (value) {
	if (isNaN(value)) return NaN;
	value = Number(value);
	if (value === 0) return value;
	if (!isFinite(value)) return value;
	if (abs(value) < 1) return (expm1(value) - expm1(-value)) / 2;
	return (exp(value - 1) - exp(-value - 1)) * e / 2;
};