How to exclude file extensions and languages from "format on save" in VSCode?

Currently in VSCode settings you can configure format on save as following:

"editor.formatOnSave": true

I want to exclude some file extensions, for example only format JavaScript but not HTML files.

You can use language specific settings to enable it for a specific language only, e.g. JavaScript:

"[javascript]": {
    "editor.formatOnSave": true
}

To disable it for a specific language, you could switch the global default to true and combine it with a language-specific false:

"editor.formatOnSave": true
"[javascript]": {
    "editor.formatOnSave": false
}

Note that language specific settings are based on language identifiers rather than directly on file extensions. There's an open feature request to allow for file extension specific settings as well.

In cases where the language ID isn't specific enough, "files.associations" could be used to remap files with a specific extension and/or in a specific directory to another ID, but this will affect syntax highlighting, code completion, etc. as well. For instance, this would work to disable formatting for JavaScript files in out directories, but they will be treated as plaintext:

"[javascript]": {
    "editor.formatOnSave": true
},
"files.associations": {
    "**/out/**/*.js": "plaintext"
}

If you came across this question as I did because you were redirected because of this question VSCode : disable formatting of a specific file (or extension) which says, this is a duplicate (I don't feel so, because I wanted it for a specific file) and you're looking for a "one-time" solution:

VS Code has a shortcut "now" (I don't know since when) for saving a file without formatting listed under the command workbench.action.files.saveWithoutFormatting - Default keybinding should be

CTRL + K CTRL + SHIFT + S 

(simply keep CTRL pressed and then type K + SHIFT + S).

On OS X the default keybinding is

CMD + k then press s