source: frontend/node_modules/webpack/lib/util/property.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/

"use strict";

const SAFE_IDENTIFIER = /^[_a-z$][_a-z$0-9]*$/i;
const RESERVED_IDENTIFIER = new Set([
        "break",
        "case",
        "catch",
        "class",
        "const",
        "continue",
        "debugger",
        "default",
        "delete",
        "do",
        "else",
        "export",
        "extends",
        "finally",
        "for",
        "function",
        "if",
        "import",
        "in",
        "instanceof",
        "new",
        "return",
        "super",
        "switch",
        "this",
        "throw",
        "try",
        "typeof",
        "var",
        "void",
        "while",
        "with",
        "enum",
        // strict mode
        "implements",
        "interface",
        "let",
        "package",
        "private",
        "protected",
        "public",
        "static",
        "yield",
        // module code
        "await",
        // skip future reserved keywords defined under ES1 till ES3
        // additional
        "null",
        "true",
        "false"
]);

/**
 * @summary Returns a valid JS property name for the given property.
 * Certain strings like "default", "null", and names with whitespace are not
 * valid JS property names, so they are returned as strings.
 * @param {string} prop property name to analyze
 * @returns {string} valid JS property name
 */
const propertyName = (prop) => {
        if (SAFE_IDENTIFIER.test(prop) && !RESERVED_IDENTIFIER.has(prop)) {
                return prop;
        }
        return JSON.stringify(prop);
};

/**
 * Returns chain of property accesses.
 * @param {ArrayLike<string>} properties properties
 * @param {number} start start index
 * @returns {string} chain of property accesses
 */
const propertyAccess = (properties, start = 0) => {
        let str = "";
        for (let i = start; i < properties.length; i++) {
                const p = properties[i];
                if (`${Number(p)}` === p) {
                        str += `[${p}]`;
                } else if (SAFE_IDENTIFIER.test(p) && !RESERVED_IDENTIFIER.has(p)) {
                        str += `.${p}`;
                } else {
                        str += `[${JSON.stringify(p)}]`;
                }
        }
        return str;
};

module.exports = {
        RESERVED_IDENTIFIER,
        SAFE_IDENTIFIER,
        propertyAccess,
        propertyName
};