Clarify return values in docs

index.d.ts

@@ -1,7 +1,7 @@
 /**
 Detect the dominant newline character of a string.
 
-@returns The detected newline or `undefined` when no newline character is found.
+@returns The detected newline or `undefined` when no newline character is found or `\n` when no dominant newline is present.
 
 @example
 ```
@@ -16,7 +16,7 @@ export function detectNewline(string: string): '\r\n' | '\n' | undefined;
 /**
 Detect the dominant newline character of a string.
 
-@returns The detected newline or `\n` when no newline character is found or the input is not a string.
+@returns The detected newline or `\n` when no newline character is found, no dominant newline is present, or the input is not a string.
 
 @example
 ```

readme.md

@@ -21,11 +21,11 @@ detectNewline('foo\nbar\nbaz\r\n');
 
 ### detectNewline(string)
 
-Returns the detected newline or `undefined` when no newline character is found.
+Returns the detected newline or `undefined` when no newline character is found or `\n` when no dominant newline is present.
 
 ### detectNewlineGraceful(unknown)
 
-Returns the detected newline or `\n` when no newline character is found or the input is not a string.
+Returns the detected newline or `\n` when no newline character is found, no dominant newline is present, or the input is not a string.
 
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