shim.js 443 Bytes
// Thanks: https://github.com/monolithed/ECMAScript-6/blob/master/ES6.js

"use strict";

var log = Math.log;

module.exports = function (value) {
	if (isNaN(value)) return NaN;
	value = Number(value);
	if (value < -1) return NaN;
	if (value === -1) return -Infinity;
	if (value === 0) return value;
	if (value === Infinity) return Infinity;

	if (value > -1.0e-8 && value < 1.0e-8) return value - value * value / 2;
	return log(1 + value);
};