source: imaps-frontend/node_modules/is-symbol/index.js@ 79a0317

'use strict';

var callBound = require('call-bound');
var $toString = callBound('Object.prototype.toString');
var hasSymbols = require('has-symbols')();
var safeRegexTest = require('safe-regex-test');

if (hasSymbols) {
        var $symToStr = callBound('Symbol.prototype.toString');
        var isSymString = safeRegexTest(/^Symbol\(.*\)$/);

        /** @type {(value: object) => value is Symbol} */
        var isSymbolObject = function isRealSymbolObject(value) {
                if (typeof value.valueOf() !== 'symbol') {
                        return false;
                }
                return isSymString($symToStr(value));
        };

        /** @type {import('.')} */
        module.exports = function isSymbol(value) {
                if (typeof value === 'symbol') {
                        return true;
                }
                if (!value || typeof value !== 'object' || $toString(value) !== '[object Symbol]') {
                        return false;
                }
                try {
                        return isSymbolObject(value);
                } catch (e) {
                        return false;
                }
        };
} else {
        /** @type {import('.')} */
        module.exports = function isSymbol(value) {
                // this environment does not support Symbols.
                return false && value;
        };
}