implementation of squeak's non-local returns and translation example of squeak to javascript

NonLocalReturn.js

// original code from http://michaelspeer.knome.net/2010/05/pattern-for-non-local-returns-in.html

var WithNonLocalReturn = function( block ){
  var nonLocalReturnException = function(){
    var value = null;
    this.setReturnValue = function( retVal ){ value = retVal };
    this.getReturnValue = function( retVal ){ return value };
  }
  
  var nonLocalReturnEx = new nonLocalReturnException();
  
  var insideStack = true;

  var leave = function( retval ){
      if( insideStack ){
          nonLocalReturnEx.setReturnValue( retval );
          throw nonLocalReturnEx;
      } else {
          throw ( ""
            + "It is invalid to call the non-local return"
            + "outside the stack of the creating WithNonLocalReturn" 
            );
      }
  };

  try {
    return block( leave );
  } catch ( e ) {
    if( e instanceof nonLocalReturnException ){
        return e.getReturnValue();
    } else {
        throw e;
    }
  } finally {
    insideStack = false;
  }
}



/* example Squeak and the corresponding JS code:


outerMethod
  [ :arg | ^arg. JSGlobal alert: 'Will never be seen' ] value: 3.
  ^2.
  

*/


block = function( f ) {
  b = {};
  b.func = f;
  b.value = function(args){ return this.func(args) };
  return b;
}


outerMethod = function(){
  return WithNonLocalReturn( function( nonLocalReturn ){  
    
    

      block(function(arg){
        nonLocalReturn(arg); // This returns from outerMethod
        alert("Will never be seen");
      }).value(3);
       
      return(2);
    
    
    
  });
}