Javascript object literal syntax I had never seen

I encountered the following code when I was working through meteor tutorial.

{
  'submit .new-task'(event) {
    // some code here
  },
}

I was very confused because I had never seen an object literal that contains some string followed by an anonymous function. After I read the MDN web docs about object initializer, I know that the code above is equivalent to the following:

{
  'submit .new-task': function(event) {
    // some code here
  },
}

The syntax looks very odd to me maybe because I am simply not got used to it.