escape-unicode/src/escape-unicode.js

Escapes Unicode characters

/*
 * Copyright (C) 2018 Alasdair Mercer
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

'use strict';

const parse = require('./parse');

/**
 * Converts all characters within <code>input</code> to Unicode escapes.
 *
 * Optionally, a <code>start</code> index can be provided to begin conversion at a specific location within
 * <code>input</code>. If <code>start</code> is not specified, <code>null</code>, or negative, the conversion will begin
 * at the start of <code>input</code>.
 *
 * Similarly, an <code>end</code> index can be provided to stop conversion at a specific location within
 * <code>input</code>. If <code>end</code> is not specified, <code>null</code>, or negative, the conversion will stop at
 * the end of <code>input</code>.
 *
 * @example
 * escapeUnicode('♥');
 * //=> "\\u2665"
 * escapeUnicode('I ♥ Unicode!');
 * //=> "\\u0049\\u0020\\u2665\\u0020\\u0055\\u006e\\u0069\\u0063\\u006f\\u0064\\u0065\\u0021"
 * escapeUnicode('I ♥ Unicode!', 2, 3);
 * //=> "\\u2665"
 * @param {?string} input - the string containing the Unicode characters to be converted (may be <code>null</code>)
 * @param {number} [start=0] - the index to begin converting characters within <code>input</code> (inclusive - may be
 * <code>null</code>)
 * @param {number} [end=input.length] - the index to stop converting characters within <code>input</code> (exclusive -
 * may be <code>null</code>)
 * @return {?string} The Unicode escapes converted from the characters within <code>input</code> or <code>null</code> if
 * <code>input</code> is <code>null</code>.
 */
function escapeUnicode(input, start, end) {
  if (input == null) {
    return input;
  }

  start = start != null && start >= 0 ? start : 0;
  end = end != null && end >= 0 ? Math.min(end, input.length) : input.length;

  let result = '';
  for (let i = start; i < end; i++) {
    result += `\\u${parse(input[i])}`;
  }

  return result;
}

module.exports = escapeUnicode;