13. A system for adding directives for JavaScript files directly into source code, the system comprising: a processor; and one or more stored sequences of instructions which, when executed by the processor, cause the processor to carry out: receiving a source file for preprocessing, wherein the source file is written in a client-side scripting language; parsing the source file; identifying a directive within the source file; associating metadata with the directive during the preprocessing such that the directive is a preprocessed directive, wherein the metadata comprises: information regarding which portions of the source file have been altered since a last preprocessing of the source file has occurred, and at least a portion of the source file in the client-side scripting language for generating at least a portion of markup language for a web page to be served to a client device using a webserver; retrieving, during the preprocessing, only the metadata associated with the preprocessed directive in the source file such that the entire source file is not retrieved; storing, during the preprocessing, the metadata associated with the preprocessed directive in a hash table; creating, during the preprocessing, a mapping for the stored metadata associated with the preprocessed directive; receiving, after the parsing, identifying, associating, retrieving, storing, and creating, a request to access the metadata associated with the preprocessed directive in the source file; and generating the at least the portion of markup language for the web page to be served to the client device in accordance with the metadata associated with the preprocessed directive from the hash table according to the mapping in response to the request.
13. A system for adding directives for JavaScript files directly into source code, the system comprising: a processor; and one or more stored sequences of instructions which, when executed by the processor, cause the processor to carry out: receiving a source file for preprocessing, wherein the source file is written in a client-side scripting language; parsing the source file; identifying a directive within the source file; associating metadata with the directive during the preprocessing such that the directive is a preprocessed directive, wherein the metadata comprises: information regarding which portions of the source file have been altered since a last preprocessing of the source file has occurred, and at least a portion of the source file in the client-side scripting language for generating at least a portion of markup language for a web page to be served to a client device using a webserver; retrieving, during the preprocessing, only the metadata associated with the preprocessed directive in the source file such that the entire source file is not retrieved; storing, during the preprocessing, the metadata associated with the preprocessed directive in a hash table; creating, during the preprocessing, a mapping for the stored metadata associated with the preprocessed directive; receiving, after the parsing, identifying, associating, retrieving, storing, and creating, a request to access the metadata associated with the preprocessed directive in the source file; and generating the at least the portion of markup language for the web page to be served to the client device in accordance with the metadata associated with the preprocessed directive from the hash table according to the mapping in response to the request. 14. The system of claim 13 , wherein the metadata associated with the directive is localization information.