传递给函数时Node.js'undefined'变量

Question

I am using the 'clouddns' module to import ~800 domain names into a Rackspace account. I keep getting an error saying the following

TypeError: Cannot call method 'forEach' of undefined
at _wrapDomains (/home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:146:17)
at /home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:209:14
at Request._callback (/home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/common.js:170:5)
at Request.self.callback (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:120:22)
at Request.EventEmitter.emit (events.js:98:17)
at Request.<anonymous> (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:555:16)
at Request.EventEmitter.emit (events.js:95:17)
at IncomingMessage.<anonymous> (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:517:14)
at IncomingMessage.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16

After looking at the library file in question (core.js) I decided to throw a couple log statements in there to see if I could figure out what was happening. Here is the code:

CloudDNS.prototype.getDomains = function getDomains(options, callback) {
    var args = Array.prototype.slice.call(arguments),
        callback = args[args.length - 1];

    if (typeof callback !== 'function') {
        throw new Error("This method requires a callback");
    }

    var self = this;
    var reqOpts = {
        method: 'GET',
        uri: this.dnsUrl('domains'),
        client: this
    }

    if ((arguments.length > 1) && (typeof arguments[0] === 'object')) {
        reqOpts.params = {
            name: args[0]
        }
    }

    this.rackspace(reqOpts, callback, function(body) {
        var result = JSON.parse(body);
        console.log(result.domains); //good here, it's an array and I can even forEach on it!
        self._wrapDomains(result.domains, callback); //undefined wtf?
        console.log(result.domains); //same as before, works brilliantly
    });
};

CloudDNS.prototype._wrapDomains = function _wrapDomains(domainArray, callback) {
    var self = this;
    var results = [];

    console.log(domainArray); //reports undefined

    domainArray.forEach(function(domain) {
        results.push(new(clouddns.Domain)(self, domain));
    });

    return callback(null, results);
}

I am weirded out by the fact that result.domains is defined before and after the method gets called, but inside that method it is 'undefined'. Can anyone shed some light on why this is happening?

Answer 1

I just checkout the source code on github. If you look at the second line in your stack trace, it's at /home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:209:14

So _wrapDomains is getting called towards the end of the file in the createDomain method (on line 209). If you investigate there, you will find out why it's calling it with null values.