javascript使用socket.io发送对象

Question

I am emiting object with socket.io

socket.emit('object',{"object":collection});

but it happens sometimes when socket.io cant emit object right now because cant reach server, socket.io remembers that emit in memory, but collection changes in meantime and on server we recieve empty object.

I tried also

socket.emit('object',function(collection){
    return {"object":collection};
}(collection)

but it goes with same empty object (in the meanwhile collection is empty.

Answer 1

Objects in JavaScript are passed by reference. Any changes outside an asynchronous function to such an object are reflected later on in the object itself.

A simple solution is to copy the object by creating a new one which has all properties (and maybe methods...) of the original.

Example for arrays would be this neat little code: [].concat(collection); . But since we're talking objects here, that won't work. With jQuery , this would be as easy as $.extend({}, collection); , but since you didn't tag it, let's make our own version of that method.

function extend( to, from, deep ) {
  // Double negation to force deep to be a boolean even if not provided. Thus: defaults to false.
  deep = !!deep;

  for( var i in from ) {
    if( deep ) {
      if( typeof from[i] == 'object' ) {
        // Array?
        if( from[i].length && typeof from[i].splice == 'function' ) {
          to[i] = [].concat(from[i]);
        }
        // nested object!
        else {
          to[i] = {};
          extend(to[i], from[i], deep);
        }
      }
      else {
        to[i] = from[i];
      }
    }
  }

  return to;
}

Applying it to socket.emit :

socket.emit('object', {
  'object' : extend({}, collection, true)
});

Note that circular references will result in an infinite loop when deep copying.