GoScrobble/web/node_modules/es5-ext/string/#/at.js

36 lines
1.0 KiB
JavaScript
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

// Based on: https://github.com/mathiasbynens/String.prototype.at
// Thanks @mathiasbynens !
"use strict";
var toInteger = require("../../number/to-integer")
, validValue = require("../../object/valid-value");
module.exports = function (pos) {
var str = String(validValue(this)), size = str.length, cuFirst, cuSecond, nextPos, len;
pos = toInteger(pos);
// Account for out-of-bounds indices
// The odd lower bound is because the ToInteger operation is
// going to round `n` to `0` for `-1 < n <= 0`.
if (pos <= -1 || pos >= size) return "";
// Second half of `ToInteger`
// eslint-disable-next-line no-bitwise
pos |= 0;
// Get the first code unit and code unit value
cuFirst = str.charCodeAt(pos);
nextPos = pos + 1;
len = 1;
if (
// Check if its the start of a surrogate pair
cuFirst >= 0xd800 &&
cuFirst <= 0xdbff && // High surrogate
size > nextPos // There is a next code unit
) {
cuSecond = str.charCodeAt(nextPos);
if (cuSecond >= 0xdc00 && cuSecond <= 0xdfff) len = 2; // Low surrogate
}
return str.slice(pos, pos + len);
};