SOURCE

let token = (function () {
    let inline = {
        comment: /^\/{2,}.*/,
        reg: /^\/.+\//,
        identifier: /^[a-zA-Z_$]+[a-zA-Z0-9_$]+/,
        str: /^[`'"]+[^`"']*[`'"]+/,
        char: /^[^\~\!@#\$\%\^\&\*\(\)\_\-\+\=\[\]\{\}\:\;\<\,\>\.\?\/\\\|\s]+/,
        space: /^\s+/,
        punct: /^[\~\!@#\%\^\&\*\(\)\-\+\=\[\]\{\}\:\;\<\,\>\.\?\/\\\|]+/,
    }
    let rule = {
        keywords: ['break', 'else', 'new', 'var',
            'case', 'finally', 'return', 'void',
            'catch', 'for', 'switch', 'while',
            'continue', 'function', 'with',
            'default', 'if', 'throw', 'delete', 'in',
            'try', 'do', 'instranceof', 'typeof', 'let',
            'const', 'debugger', 'class', 'typeof', 'break'],
        identifier: /^[a-zA-Z_$]+[a-zA-Z0-9_$]*/,
        string: /[`'"]+[^`"']*[`'"]+/,
        numeric: /^[0-9]+$/,
    }
    function colorize(str) {
        if (rule.keywords.indexOf(str) != -1) {
            return 'keyword';
        } else if (rule.numeric.test(str) || (str == 'true' || str == 'false')) {
            return 'bool';
        } else if (rule.identifier.test(str)) {
            return 'identifier';
        } else if (rule.string.test(str)) {
            return 'str';
        }
        return 'common';
    }
    function escape(str) {
        let color = colorize(str);
        return `<span class="${color}">${str.replace(/\s/g, '&nbsp;')}</span>`;
    }
    function wrap(str) {
        return `<span>${str}</span>`;
    }
    function wrapLine(str) {
        return `<div class="line">${str}</div>`;
    }
    return function split(str) {
        if (!str || typeof str != 'string') {
            return false;
        }
        let substr = str
        let cap = null
        let arr = []
        let len = 0;
        let matches = '';
        let n = 0;
        while (substr) {
            if ((cap = inline.comment.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "comment",
                };
                len = cap[0].length;
                arr.push(matches);
                substr = substr.slice(len);
            }
            if ((cap = inline.reg.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "regexp",
                };
                len = cap[0].length;
                arr.push(matches);
                substr = substr.slice(len);
            }
            if ((cap = inline.identifier.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "identifier",
                };
                len = cap[0].length;
                arr.push(matches)
                substr = substr.slice(len)
            }
            if ((cap = inline.str.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "string",
                };
                len = cap[0].length;
                arr.push(matches)
                substr = substr.slice(len)
            }
            if ((cap = inline.char.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "character",
                };
                len = cap[0].length;
                arr.push(matches)
                substr = substr.slice(len)
            }
            if ((cap = inline.space.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "space",
                };
                len = cap[0].length;
                arr.push(matches)
                substr = substr.slice(len)
            }
            if ((cap = inline.punct.exec(substr))) {
                matches = {
                    text: cap[0],
                    color: colorize(cap[0]),
                    type: "punctuation",
                };
                len = cap[0].length;
                arr.push(matches)
                substr = substr.slice(len)
            }
            n++;
            if (n > 1000) {
                break;
            }
        }
        return arr;
    }
})();

console.log(token("/a/"))

<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=, initial-scale=">
	<meta http-equiv="X-UA-Compatible" content="">
	<title></title>
</head>
<body>
	
</body>
</html>