gistfile1.txt

trigram_dict = {};
str_arr.forEach( function(e,i){
	sent = e;
word_tokens = str.split(" ");

	word_tokens.forEach( 
		function(e,i){ 
			if( i < 1 ){ return true; }
			if( i == ( word_tokens.length - 1 ) ){ return true; }
			// check if key (previous-word current-word) present
			if( !trigram_dict[ word_tokens[i-1]+' '+e] ){       
				     trigram_dict[ word_tokens[i-1]+' '+e] = [] ; 
			}
			//check if next-word available
			if( typeof(word_tokens[i+1]) != "undefined" ){ 
				trigram_dict[word_tokens[i-1]+' '+e].push(word_tokens[i+1] );
			}
		}
	);

} );