unicode-bom

A byte order mark (BOM) is the invisible character U+FEFF at the very start of a file. Some editors on Windows add it when they save as UTF-8. UTF-8 doesn't need it. It breaks a #! line, and it ends up in the middle of the output when files are joined.

By default the rule reports a file that starts with the mark.

--fix removes the mark, or adds it with "always".

Configure

Off by default. To turn it on:

[lint.rules]
"unicode-bom" = "error" # or "warn"

Every option, set to its default:

[lint.rules]
"unicode-bom" = ["error", "never"] # "always" or "never"

Examples

The mark is invisible, so a file that has one looks the same here as a file that doesn't. None of these examples has one.

Not reported:

const port = 3000;

Reported with "always", because the mark is missing:

const port = 3000;

Options

Option	What it does
"never" (default)	Report a file that starts with a byte order mark.
"always"	Report a file that doesn't start with one.