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

'use strict';

var callBound = require('call-bound');
var safeRegexTest = require('safe-regex-test');

var toStr = callBound('Object.prototype.toString');
var fnToStr = callBound('Function.prototype.toString');
var isFnRegex = safeRegexTest(/^\s*async(?:\s+function(?:\s+|\()|\s*\()/);

var hasToStringTag = require('has-tostringtag/shams')();
var getProto = require('get-proto');

var getAsyncFunc = function () { // eslint-disable-line consistent-return
        if (!hasToStringTag) {
                return false;
        }
        try {
                return Function('return async function () {}')();
        } catch (e) {
        }
};

/** @type {import('.').AsyncFunction | false} */
var AsyncFunction;

/** @type {import('.')} */
module.exports = function isAsyncFunction(fn) {
        if (typeof fn !== 'function') {
                return false;
        }
        if (isFnRegex(fnToStr(fn))) {
                return true;
        }
        if (!hasToStringTag) {
                var str = toStr(fn);
                return str === '[object AsyncFunction]';
        }
        if (!getProto) {
                return false;
        }
        if (typeof AsyncFunction === 'undefined') {
                var asyncFunc = getAsyncFunc();
                // eslint-disable-next-line no-extra-parens
                AsyncFunction = asyncFunc ? /** @type {import('.').AsyncFunction} */ (getProto(asyncFunc)) : false;
        }
        return getProto(fn) === AsyncFunction;
};