为什么多次触发此回调？

Question

I'm integrating the Google+ JS API with my website and am having a curious problem. When my login button is pressed, I have it call the following function:

function googlePlusLogin() {
    console.log("inside googlePlusLogin()");

    gapi.auth.signIn({
        'clientid' : '[id]',
        'cookiepolicy' : 'single_host_origin',
        'scope' : 'profile email',
        'callback' : function() {console.log('test');}
    });
}

The first time I click the button, the console output is:

inside googlePlusLogin()
test

As expected. However, each additional time I click on the button (triggering the above function) the number of times test prints out increments. So, for example, the second time I click the button the output is:

inside googlePlusLogin()
test
test

The third time I click the button, the output is:

inside googlePlusLogin()
test
test
test

And so on..

What is causing this behavior?

Note: I tagged this as JavaScript because I think this is probably a basic JS concept I just don't understand.

Answer 1

Quite old but I faced the same issue, so for future reference:

It seems like every time you call gapi.auth.signIn , the "callback" function is added to some list of callbacks. Thus, set the callback parameter only the first time you call gapi.auth.signIn , ie something like

function googlePlusLogin() {
  console.log("inside googlePlusLogin()");

  if(window.__callback_initialized) {
    gapi.auth.signIn({
      'clientid' : '[id]',
      'cookiepolicy' : 'single_host_origin',
      'scope' : 'profile email'
    });
  } else {
    gapi.auth.signIn({
      'clientid' : '[id]',
      'cookiepolicy' : 'single_host_origin',
      'scope' : 'profile email',
      'callback' : function() {console.log('test');}
    });
    window.__callback_initialized = true;
  }
}

modulo the DRY violation will do.