Whether you want to commit a part of your changes only or simply check your work before you commit it, one of the Git commands you probably use the most, add, can help you doing it throught its option -p (patch).

This option allows to choose the changes you want to stage.
Or word for word, from Git’s man:

Interactively choose hunks of patch between the index and the work tree and add them to the index. This gives the user a chance to review the difference before adding modified contents to the index.

This is how it works, or rather how I use it:

After executing git add -p ., git enters an interactive mode, from where many actions can be taken. Below are the ones I use the most.

• If the diff is too long, you can try splitting it with s. That will split it into the smallest possible parts.
• If you want to stage the diff, simply choose yes.
• Otherwise, say no.
• When the whole diff has been viewed, the interactive mode will quit automatically. You can do it yourself tough, through the classic ^C, or by selecting q.
  Note that this will simply quit the interactive mode and won’t undo your actions.

Feel free to ask ? about the other commands meaning, they might be useful in some cases.

git add -p your best friend to review your code and not to commit stuff like console.log().
Make the most of it!