Source: strings.js

  1. 'use strict'
  3. /**
  4.  * @module strings
  5.  */
  6. export const strings = {};
  8. /**
  9.  * Escapes characters with special meaning in {@link RegExp}.
  10.  *
  11.  * @param {string} str the string to escape.
  12.  * @return {string} the escaped string.
  13.  * @memberOf module:strings
  14.  */
  15. strings.escapeCharactersWithSpecialMeaningInRegExp = function (str) {
  16.   return str ? ('' + str).replace(/[.*+?^${}()|[\]\\]/g, '\\$&' /* the whole matched string */) : '';
  17. }
  19. /**
  20.  * Converts a string to a {@link RegExp} literal.
  21.  *
  22.  * @param {string} str the string to convert.
  23.  * @param {string} flags the flags of the regular expression.
  24.  * @return {RegExp} a {@link RegExp}.
  25.  * @memberOf module:strings
  26.  */
  27. strings.toRegExp = function (str, flags) {
  29.   // As of 2020-01-06, the DOT_ALL flag is not available on Firefox
  30.   // If truly needed, use [^]* that reads "match any character that is not nothing"
  31.   const newFlags = flags ? flags : 'im';
  32.   const escapedString = strings.escapeCharactersWithSpecialMeaningInRegExp(str).split(/[\s\u00a0]+/).join(
  33.     '(\\s|\u00a0)*');
  34.   return new RegExp(escapedString, newFlags);
  35. }
  37. /**
  38.  * Removes diacritical marks from a string.
  39.  *
  40.  * @param {string} str the string to clean.
  41.  * @param {boolean} preserveStringLength true iif the original string length must be preserved.
  42.  * @return {string} the cleaned text i.e. without diacritical marks.
  43.  * @memberOf module:strings
  44.  * @preserve The code is extracted from https://web.archive.org/web/20121231230126/http://lehelk.com:80/2011/05/06/script-to-remove-diacritics/.
  45.  */
  46. strings.removeDiacritics = function (str, preserveStringLength) {
  48.   str = str ? '' + str : '';
  50.   const diacritics = [{
  51.     base: 'A',
  52.     letters: /[\u0041\u24B6\uFF21\u00C0\u00C1\u00C2\u1EA6\u1EA4\u1EAA\u1EA8\u00C3\u0100\u0102\u1EB0\u1EAE\u1EB4\u1EB2\u0226\u01E0\u00C4\u01DE\u1EA2\u00C5\u01FA\u01CD\u0200\u0202\u1EA0\u1EAC\u1EB6\u1E00\u0104\u023A\u2C6F]/g
  53.   }, {
  54.     base: 'B', letters: /[\u0042\u24B7\uFF22\u1E02\u1E04\u1E06\u0243\u0182\u0181]/g
  55.   }, {
  56.     base: 'C', letters: /[\u0043\u24B8\uFF23\u0106\u0108\u010A\u010C\u00C7\u1E08\u0187\u023B\uA73E]/g
  57.   }, {
  58.     base: 'D', letters: /[\u0044\u24B9\uFF24\u1E0A\u010E\u1E0C\u1E10\u1E12\u1E0E\u0110\u018B\u018A\u0189\uA779]/g
  59.   }, {
  60.     base: 'E',
  61.     letters: /[\u0045\u24BA\uFF25\u00C8\u00C9\u00CA\u1EC0\u1EBE\u1EC4\u1EC2\u1EBC\u0112\u1E14\u1E16\u0114\u0116\u00CB\u1EBA\u011A\u0204\u0206\u1EB8\u1EC6\u0228\u1E1C\u0118\u1E18\u1E1A\u0190\u018E]/g
  62.   }, {
  63.     base: 'F', letters: /[\u0046\u24BB\uFF26\u1E1E\u0191\uA77B]/g
  64.   }, {
  65.     base: 'G', letters: /[\u0047\u24BC\uFF27\u01F4\u011C\u1E20\u011E\u0120\u01E6\u0122\u01E4\u0193\uA7A0\uA77D\uA77E]/g
  66.   }, {
  67.     base: 'H', letters: /[\u0048\u24BD\uFF28\u0124\u1E22\u1E26\u021E\u1E24\u1E28\u1E2A\u0126\u2C67\u2C75\uA78D]/g
  68.   }, {
  69.     base: 'I',
  70.     letters: /[\u0049\u24BE\uFF29\u00CC\u00CD\u00CE\u0128\u012A\u012C\u0130\u00CF\u1E2E\u1EC8\u01CF\u0208\u020A\u1ECA\u012E\u1E2C\u0197]/g
  71.   }, {base: 'J', letters: /[\u004A\u24BF\uFF2A\u0134\u0248]/g}, {
  72.     base: 'K', letters: /[\u004B\u24C0\uFF2B\u1E30\u01E8\u1E32\u0136\u1E34\u0198\u2C69\uA740\uA742\uA744\uA7A2]/g
  73.   }, {
  74.     base: 'L',
  75.     letters: /[\u004C\u24C1\uFF2C\u013F\u0139\u013D\u1E36\u1E38\u013B\u1E3C\u1E3A\u0141\u023D\u2C62\u2C60\uA748\uA746\uA780]/g
  76.   }, {
  77.     base: 'M', letters: /[\u004D\u24C2\uFF2D\u1E3E\u1E40\u1E42\u2C6E\u019C]/g
  78.   }, {
  79.     base: 'N',
  80.     letters: /[\u004E\u24C3\uFF2E\u01F8\u0143\u00D1\u1E44\u0147\u1E46\u0145\u1E4A\u1E48\u0220\u019D\uA790\uA7A4]/g
  81.   }, {
  82.     base: 'O',
  83.     letters: /[\u004F\u24C4\uFF2F\u00D2\u00D3\u00D4\u1ED2\u1ED0\u1ED6\u1ED4\u00D5\u1E4C\u022C\u1E4E\u014C\u1E50\u1E52\u014E\u022E\u0230\u00D6\u022A\u1ECE\u0150\u01D1\u020C\u020E\u01A0\u1EDC\u1EDA\u1EE0\u1EDE\u1EE2\u1ECC\u1ED8\u01EA\u01EC\u00D8\u01FE\u0186\u019F\uA74A\uA74C]/g
  84.   }, {
  85.     base: 'P', letters: /[\u0050\u24C5\uFF30\u1E54\u1E56\u01A4\u2C63\uA750\uA752\uA754]/g
  86.   }, {
  87.     base: 'Q', letters: /[\u0051\u24C6\uFF31\uA756\uA758\u024A]/g
  88.   }, {
  89.     base: 'R',
  90.     letters: /[\u0052\u24C7\uFF32\u0154\u1E58\u0158\u0210\u0212\u1E5A\u1E5C\u0156\u1E5E\u024C\u2C64\uA75A\uA7A6\uA782]/g
  91.   }, {
  92.     base: 'S',
  93.     letters: /[\u0053\u24C8\uFF33\u1E9E\u015A\u1E64\u015C\u1E60\u0160\u1E66\u1E62\u1E68\u0218\u015E\u2C7E\uA7A8\uA784]/g
  94.   }, {
  95.     base: 'T', letters: /[\u0054\u24C9\uFF34\u1E6A\u0164\u1E6C\u021A\u0162\u1E70\u1E6E\u0166\u01AC\u01AE\u023E\uA786]/g
  96.   }, {
  97.     base: 'U',
  98.     letters: /[\u0055\u24CA\uFF35\u00D9\u00DA\u00DB\u0168\u1E78\u016A\u1E7A\u016C\u00DC\u01DB\u01D7\u01D5\u01D9\u1EE6\u016E\u0170\u01D3\u0214\u0216\u01AF\u1EEA\u1EE8\u1EEE\u1EEC\u1EF0\u1EE4\u1E72\u0172\u1E76\u1E74\u0244]/g
  99.   }, {
  100.     base: 'V', letters: /[\u0056\u24CB\uFF36\u1E7C\u1E7E\u01B2\uA75E\u0245]/g
  101.   }, {
  102.     base: 'W', letters: /[\u0057\u24CC\uFF37\u1E80\u1E82\u0174\u1E86\u1E84\u1E88\u2C72]/g
  103.   }, {base: 'X', letters: /[\u0058\u24CD\uFF38\u1E8A\u1E8C]/g}, {
  104.     base: 'Y', letters: /[\u0059\u24CE\uFF39\u1EF2\u00DD\u0176\u1EF8\u0232\u1E8E\u0178\u1EF6\u1EF4\u01B3\u024E\u1EFE]/g
  105.   }, {
  106.     base: 'Z', letters: /[\u005A\u24CF\uFF3A\u0179\u1E90\u017B\u017D\u1E92\u1E94\u01B5\u0224\u2C7F\u2C6B\uA762]/g
  107.   }, {
  108.     base: 'a',
  109.     letters: /[\u0061\u24D0\uFF41\u1E9A\u00E0\u00E1\u00E2\u1EA7\u1EA5\u1EAB\u1EA9\u00E3\u0101\u0103\u1EB1\u1EAF\u1EB5\u1EB3\u0227\u01E1\u00E4\u01DF\u1EA3\u00E5\u01FB\u01CE\u0201\u0203\u1EA1\u1EAD\u1EB7\u1E01\u0105\u2C65\u0250]/g
  110.   }, {
  111.     base: 'b', letters: /[\u0062\u24D1\uFF42\u1E03\u1E05\u1E07\u0180\u0183\u0253]/g
  112.   }, {
  113.     base: 'c', letters: /[\u0063\u24D2\uFF43\u0107\u0109\u010B\u010D\u00E7\u1E09\u0188\u023C\uA73F\u2184]/g
  114.   }, {
  115.     base: 'd', letters: /[\u0064\u24D3\uFF44\u1E0B\u010F\u1E0D\u1E11\u1E13\u1E0F\u0111\u018C\u0256\u0257\uA77A]/g
  116.   }, {
  117.     base: 'e',
  118.     letters: /[\u0065\u24D4\uFF45\u00E8\u00E9\u00EA\u1EC1\u1EBF\u1EC5\u1EC3\u1EBD\u0113\u1E15\u1E17\u0115\u0117\u00EB\u1EBB\u011B\u0205\u0207\u1EB9\u1EC7\u0229\u1E1D\u0119\u1E19\u1E1B\u0247\u025B\u01DD]/g
  119.   }, {
  120.     base: 'f', letters: /[\u0066\u24D5\uFF46\u1E1F\u0192\uA77C]/g
  121.   }, {
  122.     base: 'g', letters: /[\u0067\u24D6\uFF47\u01F5\u011D\u1E21\u011F\u0121\u01E7\u0123\u01E5\u0260\uA7A1\u1D79\uA77F]/g
  123.   }, {
  124.     base: 'h', letters: /[\u0068\u24D7\uFF48\u0125\u1E23\u1E27\u021F\u1E25\u1E29\u1E2B\u1E96\u0127\u2C68\u2C76\u0265]/g
  125.   }, {
  126.     base: 'i',
  127.     letters: /[\u0069\u24D8\uFF49\u00EC\u00ED\u00EE\u0129\u012B\u012D\u00EF\u1E2F\u1EC9\u01D0\u0209\u020B\u1ECB\u012F\u1E2D\u0268\u0131]/g
  128.   }, {
  129.     base: 'j', letters: /[\u006A\u24D9\uFF4A\u0135\u01F0\u0249]/g
  130.   }, {
  131.     base: 'k', letters: /[\u006B\u24DA\uFF4B\u1E31\u01E9\u1E33\u0137\u1E35\u0199\u2C6A\uA741\uA743\uA745\uA7A3]/g
  132.   }, {
  133.     base: 'l',
  134.     letters: /[\u006C\u24DB\uFF4C\u0140\u013A\u013E\u1E37\u1E39\u013C\u1E3D\u1E3B\u017F\u0142\u019A\u026B\u2C61\uA749\uA781\uA747]/g
  135.   }, {
  136.     base: 'm', letters: /[\u006D\u24DC\uFF4D\u1E3F\u1E41\u1E43\u0271\u026F]/g
  137.   }, {
  138.     base: 'n',
  139.     letters: /[\u006E\u24DD\uFF4E\u01F9\u0144\u00F1\u1E45\u0148\u1E47\u0146\u1E4B\u1E49\u019E\u0272\u0149\uA791\uA7A5]/g
  140.   }, {
  141.     base: 'o',
  142.     letters: /[\u006F\u24DE\uFF4F\u00F2\u00F3\u00F4\u1ED3\u1ED1\u1ED7\u1ED5\u00F5\u1E4D\u022D\u1E4F\u014D\u1E51\u1E53\u014F\u022F\u0231\u00F6\u022B\u1ECF\u0151\u01D2\u020D\u020F\u01A1\u1EDD\u1EDB\u1EE1\u1EDF\u1EE3\u1ECD\u1ED9\u01EB\u01ED\u00F8\u01FF\u0254\uA74B\uA74D\u0275]/g
  143.   }, {
  144.     base: 'p', letters: /[\u0070\u24DF\uFF50\u1E55\u1E57\u01A5\u1D7D\uA751\uA753\uA755]/g
  145.   }, {
  146.     base: 'q', letters: /[\u0071\u24E0\uFF51\u024B\uA757\uA759]/g
  147.   }, {
  148.     base: 'r',
  149.     letters: /[\u0072\u24E1\uFF52\u0155\u1E59\u0159\u0211\u0213\u1E5B\u1E5D\u0157\u1E5F\u024D\u027D\uA75B\uA7A7\uA783]/g
  150.   }, {
  151.     base: 's',
  152.     letters: /[\u0073\u24E2\uFF53\u00DF\u015B\u1E65\u015D\u1E61\u0161\u1E67\u1E63\u1E69\u0219\u015F\u023F\uA7A9\uA785\u1E9B]/g
  153.   }, {
  154.     base: 't',
  155.     letters: /[\u0074\u24E3\uFF54\u1E6B\u1E97\u0165\u1E6D\u021B\u0163\u1E71\u1E6F\u0167\u01AD\u0288\u2C66\uA787]/g
  156.   }, {
  157.     base: 'u',
  158.     letters: /[\u0075\u24E4\uFF55\u00F9\u00FA\u00FB\u0169\u1E79\u016B\u1E7B\u016D\u00FC\u01DC\u01D8\u01D6\u01DA\u1EE7\u016F\u0171\u01D4\u0215\u0217\u01B0\u1EEB\u1EE9\u1EEF\u1EED\u1EF1\u1EE5\u1E73\u0173\u1E77\u1E75\u0289]/g
  159.   }, {
  160.     base: 'v', letters: /[\u0076\u24E5\uFF56\u1E7D\u1E7F\u028B\uA75F\u028C]/g
  161.   }, {
  162.     base: 'w', letters: /[\u0077\u24E6\uFF57\u1E81\u1E83\u0175\u1E87\u1E85\u1E98\u1E89\u2C73]/g
  163.   }, {base: 'x', letters: /[\u0078\u24E7\uFF58\u1E8B\u1E8D]/g}, {
  164.     base: 'y',
  165.     letters: /[\u0079\u24E8\uFF59\u1EF3\u00FD\u0177\u1EF9\u0233\u1E8F\u00FF\u1EF7\u1E99\u1EF5\u01B4\u024F\u1EFF]/g
  166.   }, {
  167.     base: 'z', letters: /[\u007A\u24E9\uFF5A\u017A\u1E91\u017C\u017E\u1E93\u1E95\u01B6\u0225\u0240\u2C6C\uA763]/g
  168.   }];
  170.   if (preserveStringLength === undefined || preserveStringLength === true) {
  171.     diacritics.push({base: 'AA', letters: /\uA732/g}, {base: 'AE', letters: /[\u00C6\u01FC\u01E2]/g},
  172.       {base: 'AO', letters: /\uA734/g}, {base: 'AU', letters: /\uA736/g}, {base: 'AV', letters: /[\uA738\uA73A]/g},
  173.       {base: 'AY', letters: /\uA73C/g}, {base: 'DZ', letters: /[\u01F1\u01C4]/g},
  174.       {base: 'Dz', letters: /[\u01F2\u01C5]/g}, {base: 'LJ', letters: /\u01C7/g}, {base: 'Lj', letters: /\u01C8/g},
  175.       {base: 'NJ', letters: /\u01CA/g}, {base: 'Nj', letters: /\u01CB/g}, {base: 'OI', letters: /\u01A2/g},
  176.       {base: 'OO', letters: /\uA74E/g}, {base: 'OU', letters: /\u0222/g}, {base: 'TZ', letters: /\uA728/g},
  177.       {base: 'VY', letters: /\uA760/g}, {base: 'aa', letters: /\uA733/g},
  178.       {base: 'ae', letters: /[\u00E6\u01FD\u01E3]/g}, {base: 'ao', letters: /\uA735/g},
  179.       {base: 'au', letters: /\uA737/g}, {base: 'av', letters: /[\uA739\uA73B]/g}, {base: 'ay', letters: /\uA73D/g},
  180.       {base: 'dz', letters: /[\u01F3\u01C6]/g}, {base: 'hv', letters: /\u0195/g}, {base: 'lj', letters: /\u01C9/g},
  181.       {base: 'nj', letters: /\u01CC/g}, {base: 'oi', letters: /\u01A3/g}, {base: 'ou', letters: /\u0223/g},
  182.       {base: 'oo', letters: /\uA74F/g}, {base: 'tz', letters: /\uA729/g}, {base: 'vy', letters: /\uA761/g});
  183.   }
  185.   for (let i = 0; i < diacritics.length; i++) {
  186.     str = str.replace(diacritics[i].letters, diacritics[i].base);
  187.   }
  188.   return str;
  189. }
  191. /**
  192.  * The Pattern type.
  193.  *
  194.  * @param {RegExp} regexp the pattern to match.
  195.  * @param {string} color the highlight color as a hexadecimal string.
  196.  * @memberOf module:strings
  197.  * @constructor
  198.  * @struct
  199.  * @final
  200.  */
  201. strings.Pattern = function (regexp, color) {
  202.   this.regexp = regexp;
  203.   this.color = color;
  204. }
  206. /**
  207.  * The Highlight type.
  208.  *
  209.  * @param {string} matchedText the matched text fragment.
  210.  * @param {number} matchedPage the page number (1-based) from which the snippet was extracted.
  211.  * @param {string} rawSnippet a snippet of text surrounding the matched text fragment (about 300 characters).
  212.  * @param {string} highlightedSnippet a snippet of text surrounding the matched and highlighted text fragment (about 300 characters).
  213.  * @memberOf module:strings
  214.  * @constructor
  215.  * @struct
  216.  * @final
  217.  */
  218. strings.Highlight = function (matchedText, matchedPage, rawSnippet, highlightedSnippet) {
  219.   this.matchedText = matchedText;
  220.   this.matchedPage = matchedPage;
  221.   this.rawSnippet = rawSnippet
  222.   this.highlightedSnippet = highlightedSnippet;
  223. }
  225. /**
  226.  * The HighlightedText type.
  227.  *
  228.  * @param {string} text the whole text, highlighted.
  229.  * @param {Array<strings.Highlight>} snippets the snippet associated with each highlighted text fragment.
  230.  * @memberOf module:strings
  231.  * @constructor
  232.  * @struct
  233.  * @final
  234.  */
  235. strings.HighlightedText = function (text, snippets) {
  236.   this.text = text;
  237.   this.snippets = snippets;
  238. }
  240. /**
  241.  * Highlights all occurrences of a given set of patterns in a string.
  242.  *
  243.  * @param {string} text the text to highlight.
  244.  * @param {Array<strings.Pattern>} patterns a set of patterns to match and highlight.
  245.  * @return {strings.HighlightedText} the highlighted text.
  246.  * @memberOf module:strings
  247.  */
  248. strings.highlight = function (text, patterns) {
  250.   text = text ? '' + text : '';
  252.   if (!patterns || patterns.length <= 0 || strings.isNullOrBlank(text)) {
  253.     return new strings.HighlightedText(text, []);
  254.   }
  256.   let highlightedText = text;
  257.   text = strings.removeDiacritics(text, true);
  259.   if (text.length !== highlightedText.length) {
  260.     highlightedText = text;
  261.   }
  262.   const highlights = patterns.flatMap(pattern => {
  264.     const matcher = pattern.regexp;
  265.     const matches = [];
  266.     let match = null;
  268.     while (match = matcher.exec(text)) {
  269.       matches.push({
  270.         start: match.index, end: match.index + match[0].length, color: pattern.color
  271.       });
  272.     }
  273.     return matches;
  274.   }).sort((a, b) => {
  275.     if (a.start < b.start) {
  276.       return 1;
  277.     }
  278.     if (a.start > b.start) {
  279.       return -1;
  280.     }
  281.     return 0;
  282.   }).map(position => {
  284.     // TODO : deal with overlaps?
  285.     const prefix = highlightedText.substring(0, position.start);
  286.     const infix = highlightedText.substring(position.start, position.end);
  287.     const suffix = highlightedText.substring(position.end);
  289.     highlightedText = `${prefix}<mark style="border-radius:3px;background:${position.color}">${infix}</mark>${suffix}`;
  291.     const begin = Math.max(0, prefix.length - 50);
  292.     const end = Math.min(150, suffix.length);
  293.     const rawSnippet = `${prefix.substring(begin)}${infix}${suffix.substring(0, end)}`;
  294.     let highlightedSnippet = `${prefix.substring(
  295.       begin)}<mark style="border-radius:3px;background:${position.color}">${infix}</mark>${suffix.substring(0, end)}`;
  296.     const pages = prefix.split('\f' /* page separator */).map((page, index) => index);
  297.     const beginMark = highlightedSnippet.lastIndexOf('<m');
  298.     const endMark = highlightedSnippet.lastIndexOf('</mark>');
  300.     if (beginMark && (!endMark || beginMark > endMark)) {
  301.       highlightedSnippet = highlightedSnippet.substring(0, beginMark);
  302.     }
  303.     return new strings.Highlight(infix, pages.length, rawSnippet, highlightedSnippet);
  304.   });
  305.   return new strings.HighlightedText(highlightedText, highlights);
  306. }
  308. /**
  309.  * Returns true iif a string is either null or blank, false otherwise.
  310.  *
  311.  * @param {string} str the string to check.
  312.  * @return {boolean} true if the string is null or blank, false otherwise.
  313.  * @memberOf module:strings
  314.  */
  315. strings.isNullOrBlank = function (str) {
  316.   return !(typeof str === 'string' && str.trim() !== '');
  317. }
  319. /**
  320.  * Prepends '0' to a string or number until a given length is reached.
  321.  *
  322.  * @param {string|number} str a string or number.
  323.  * @param {number} targetLength the string target length.
  324.  * @return {string} a padded string.
  325.  * @memberOf module:strings
  326.  */
  327. strings.pad = function (str, targetLength) {
  328.   return (str ? '' + str : '').padStart(targetLength, '0');
  329. }
  331. /**
  332.  * Removes all '0' from the beginning of a string.
  333.  *
  334.  * @param {string} str a string.
  335.  * @return {string} an un-padded string.
  336.  * @memberOf module:strings
  337.  */
  338. strings.unpad = function (str) {
  339.   str = str ? '' + str : '';
  340.   let i = 0;
  341.   for (; i < str.length && str[i] === '0'; i++) {
  342.   }
  343.   return str.substring(i);
  344. }
  346. /**
  347.  * Checks if a string represents a numeric value.
  348.  *
  349.  * @param {string} str the string to check.
  350.  * @return {boolean} true if the string is a number, false otherwise.
  351.  * @memberOf module:strings
  352.  * @preserve The code is extracted from https://stackoverflow.com/a/175787.
  353.  */
  354. strings.isNumeric = function (str) {
  355.   return typeof str === 'string' ? !isNaN(str) && !isNaN(parseFloat(str)) : false;
  356. }
  358. /**
  359.  * Formats null or blank values.
  360.  *
  361.  * @param {string|number} str the value to format.
  362.  * @param {string} defaultValue the string to return if the value is either null or empty.
  363.  * @return {string} the formatted value.
  364.  */
  365. strings.formatNullOrBlank = function (str, defaultValue) {
  366.   str = str ? '' + str : '';
  367.   return strings.isNullOrBlank(str) ? defaultValue : str;
  368. }
  370. /**
  371.  * Returns true iif a string starts with 'MASKED_', false otherwise.
  372.  *
  373.  * @param {string} str the string to check.
  374.  * @return {boolean} true iif the string starts with 'MASKED_', false otherwise.
  375.  */
  376. strings.isMasked = function (str) {
  377.   return typeof str === 'string' ? str.trim().toUpperCase().startsWith('MASKED_') : false;
  378. }
  380. /**
  381.  * Convert a string from camel case to snake case.
  382.  *
  383.  * @param {string} str the string in camel case.
  384.  * @returns {string} the string in snake case.
  385.  */
  386. strings.camelToSnakeCase = function (str) {
  387.   return typeof str === 'string' ? str.replace(/[A-Z]/g,
  388.     (letter, idx) => idx === 0 ? letter.toLowerCase() : `_${letter.toLowerCase()}`) : null;
  389. }
  391. /**
  392.  * Convert a string from snake case to camel case.
  393.  *
  394.  * @param {string} str the string in snake case.
  395.  * @returns {string} the string in camel case.
  396.  */
  397. strings.snakeCaseToCamelCase = function (str) {
  398.   return typeof str === 'string' ? str.replace(/_[a-z]/g,
  399.     (group, idx) => idx === 0 ? group.replace('_', '') : group.toUpperCase().replace('_', '')) : null;
  400. }