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9-regular-expressions/05-regexp-multiline-mode/article.md

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+# Multiline mode of anchors ^ $, flag "m"
+
+The multiline mode is enabled by the flag `pattern:m`.
+
+It only affects the behavior of `pattern:^` and `pattern:$`.
+
+In the multiline mode they match not only at the beginning and the end of the string, but also at start/end of line.
+
+## Searching at line start ^
+
+In the example below the text has multiple lines. The pattern `pattern:/^\d/gm` takes a digit from the beginning of each line:
+
+```js run
+let str = `1st place: Winnie
+2nd place: Piglet
+3rd place: Eeyore`;
+
+*!*
+alert( str.match(/^\d/gm) ); // 1, 2, 3
+*/!*
+```
+
+Without the flag `pattern:m` only the first digit is matched:
+
+```js run
+let str = `1st place: Winnie
+2nd place: Piglet
+3rd place: Eeyore`;
+
+*!*
+alert( str.match(/^\d/g) ); // 1
+*/!*
+```
+
+That's because by default a caret `pattern:^` only matches at the beginning of the text, and in the multiline mode -- at the start of any line.
+
+```smart
+"Start of a line" formally means "immediately after a line break": the test  `pattern:^` in multiline mode matches at all positions preceeded by a newline character `\n`.
+
+And at the text start.
+```
+
+## Searching at line end $
+
+The dollar sign `pattern:$` behaves similarly.
+
+The regular expression `pattern:\d$` finds the last digit in every line
+
+```js run
+let str = `Winnie: 1
+Piglet: 2
+Eeyore: 3`;
+
+alert( str.match(/\d$/gm) ); // 1,2,3
+```
+
+Without the flag `m`, the dollar `pattern:$` would only match the end of the whole text, so only the very last digit would be found.
+
+```smart
+"End of a line" formally means "immediately before a line break": the test  `pattern:^` in multiline mode matches at all positions succeeded by a newline character `\n`.
+
+And at the text end.
+```
+
+## Searching for \n instead of ^ $
+
+To find a newline, we can use not only anchors `pattern:^` and `pattern:$`, but also the newline character `\n`.
+
+What's the difference? Let's see an example.
+
+Here we search for `pattern:\d\n` instead of `pattern:\d$`:
+
+```js run
+let str = `Winnie: 1
+Piglet: 2
+Eeyore: 3`;
+
+alert( str.match(/\d\n/gm) ); // 1\n,2\n
+```
+
+As we can see, there are 2 matches instead of 3.
+
+That's because there's no newline after `subject:3` (there's text end though, so it matches `pattern:$`).
+
+Another difference: now every match includes a newline character `match:\n`. Unlike the anchors `pattern:^` `pattern:$`, that only test the condition (start/end of a line), `\n` is a character, so it becomes a part of the result.
+
+So, a `\n` in the pattern is used when we need newline characters in the result, while anchors are used to find something at the beginning/end of a line.