src/observations.js
function(context, expression, onChange, callbackContext) {
    var observer = this.createObserver(expression, onChange, callbackContext || context);
    observer.bind(context);
    return observer;
  }
function(context, expression, onChange, callbackContext) {
    var observer = this.createObserver(expression, onChange, callbackContext || context);
    observer.bind(context);
    return observer;
  }
function ( context , expression , onChange , callbackContext ) { var observer = this . createObserver ( expression , onChange , callbackContext || context ) ; observer . bind ( context ) ; return observer ; }
Observes any changes to the result of the expression on the context object and calls the callback.
@param {Object} context The context to bind the expression against
@param {String} expression The expression to observe
@param {Function} onChange The function which will be called when the expression value changes
@return {Observer} The observer created
Observes any changes to the result of the expression on the context object and calls the callback .