为什么我的javascript对象的值未定义？

Question

I keep getting undefined when I attempt to output the objects value via chrome console. Code:

ws.on('message', function(message) {
     var JSONobj = {"cmd":"updatesb","name":"TestName"};
     console.log('JSON Name Value: %s', message.name); //<--does not work
     console.log('JSON Name Value: %s', JSONobj.name); //<----WORKS!!!!
});

The message argument in ws.on passes {"cmd":"updatesb","name":"TestName"} via websocket communication. The first console output is undefined. The second output is TestName. Why is message.name undefined when it should have a value of TestName and how do I get the value from message.name?

Answer 1

It sounds like your message parameter is a string, not an object.

You can parse that string as JSON by calling JSON.parse() .

Answer 2

Try:

 message.name = 'xxx';
 console.log('JSON Name Value: %s', message.name);

to see if the message.name succeeds. As others pointed out, message is most likely not what you think.

Try also console.log(message); and examine the output.

Also, it may be that the on handler receives more then just the message so the handler should in fact look like function(something_else, message) , but it is hard to know without knowing what ws is.