| // Based on: https://github.com/mathiasbynens/String.prototype.codePointAt |
| // Thanks @mathiasbynens ! |
| |
| "use strict"; |
| |
| var toInteger = require("../../../number/to-integer") |
| , validValue = require("../../../object/valid-value"); |
| |
| module.exports = function (pos) { |
| var str = String(validValue(this)), length = str.length, first, second; |
| pos = toInteger(pos); |
| |
| // Account for out-of-bounds indices: |
| if (pos < 0 || pos >= length) return undefined; |
| |
| // Get the first code unit |
| first = str.charCodeAt(pos); |
| if (first >= 0xd800 && first <= 0xdbff && length > pos + 1) { |
| second = str.charCodeAt(pos + 1); |
| if (second >= 0xdc00 && second <= 0xdfff) { |
| // http://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae |
| return (first - 0xd800) * 0x400 + second - 0xdc00 + 0x10000; |
| } |
| } |
| return first; |
| }; |