Ember.streams.Ember.stream.chain()

Generate a new stream by providing a source stream and a function that can be used to transform the stream's value. In the case of a non-stream object, returns the result of the function.

The value to transform would typically be available to the function you pass to chain() via scope. For example:

    let source = ...;  // stream returning a number
                           // or a numeric (non-stream) object
    let result = chain(source, function() {
      let currentValue = read(source);
      return currentValue + 1;
    });

In the example, result is a stream if source is a stream, or a number of source was numeric.