CODEWITHSUNDEEP
javascriptbackbone.js
user1637281
user1637281

Reputation:

Events - main purpose of eventsApi()?

Conceptually, what does eventsApi() do? It is private to Backbone but used in 4 public event methods - on(), once(), off(), and trigger().

In each, if it returns a non-truthy value the method calling it will exit "early".

One thing it does, is determine if the second part of the calling method will execute. If name is not truthy or is not a complex type ( object or space separated strings ) it will return a true allowing the second part of the method to run.

What is the main purpose of the eventsApi function, conceptually, as I have tried to describe what it does functionally/logically?

eventsAPI

  var eventsApi = function(obj, action, name, rest) {
    if (!name) return true;
    if (typeof name === 'object') {
      for (var key in name) {
        obj[action].apply(obj, [key, name[key]].concat(rest));
      }
    } else if (eventSplitter.test(name)) {
      var names = name.split(eventSplitter);
      for (var i = 0, l = names.length; i < l; i++) {
        obj[action].apply(obj, [names[i]].concat(rest));
      }
    } else {
      return true;
    }
  };

Upvotes: 2

Views: 213

Answers (1)

Paul Hoenecke
Paul Hoenecke

Reputation: 5060

Like the comment in the source says, it implements the more fancy uses of the Events API.

// Implement fancy features of the Events API such as multiple event
// names `"change blur"` and jQuery-style event maps `{change: action}`
// in terms of the existing API.

So, when you use the Events API with an event map:

book.on({
  "change:title": titleView.update,
  "change:author": authorPane.update,
  "destroy": bookView.remove
});

The eventsApi function detects that the input is an object, and calls on again for each of the properties passed in.

The other case it handles is space separated events:

book.on("change:title change:author", ...);

In this case, eventsApi function detects this situation and, again, calls on once for each of the events passed in.

Upvotes: 1

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