why I can't send function to content script with sendMessage

Question

I'm sending the following message to content script:

chrome.tabs.sendMessage(activeTabId, {
    name:'executePageScript', 
    word:word, 
    isFirst:isFirst, 
    jq: function() {}
});

And listening to it in content script:

chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {})

The problem is that message object contains all keys except for the jq which holds reference to the function expression. If I change function expression to numerical or string literal, like this jq:3 or jq:"string", then the jq key is available in the message object. So it seems that I can't send function expressions (pointers to functions) to content script. Is it true? Or am I missing something?

Answer 1

chrome.tabs.sendMessage works with messages as with JSON objects. (It serialise data before passing)

JSON specification not include functions i.e. all functions will be filtered before JSON serialisation.

The simple example:

var obj = {
  a: '1',
  b: 2,
  c: undefined,
  d: null,
  e: new Date(),
  f: function(){}
}
var str = JSON.stringify(obj);

UPDATE (workaround):

chrome.tabs.sendMessage(activeTabId, {
    name:'executePageScript', 
    word:word, 
    isFirst:isFirst, 
    jq: 'actionName1',
    jqParams: [1,2,3]
});

Other place:

runtimeRouter = {
  actionName1: function(a,b,c){
    console.log(arguments);
  }
}
runtime.onMessage(function(message, sender){
  if (message.jq && typeof runtimeRouter[message.jq] === 'function') {
    runtimeRouter[message.jq].apply(/*some context or null*/null, message.jqParams || []);
  }
});