CodeQL documentation

Lines of code in files

ID: js/lines-of-code-in-files
Kind: treemap
   - maintainability

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There are a number of problems associated with a high number of lines of code:

  • It can be difficult to understand and maintain, even with good tool support.

  • It increases the likelihood of multiple developers needing to work on the same file at once, and it therefore increases the likelihood of merge conflicts.

  • It may increase network traffic if you use a version control system that requires the whole file to be transmitted even for a tiny change.

  • It may arise as a result of bundling many unrelated things into the same file, and so it can indicate weak code organization.


The solution depends on the reason for the high number of lines:

  • If the file contains one or more very large functions, you should decompose them into smaller functions by means of the Extract Function refactoring.

  • If the file contains many smaller functions, you should try to split up the file into multiple smaller files.

  • If the file has been automatically generated by a tool, no changes are required because the file will not be maintained by a programmer.


  • M. Fowler, Refactoring. Addison-Wesley, 1999.

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