78 lines
2.1 KiB
Markdown
78 lines
2.1 KiB
Markdown
# Multiline mode, flag "m"
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The multiline mode is enabled by the flag `pattern:/.../m`.
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[cut]
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It only affects the behavior of `pattern:^` and `pattern:$`.
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In the multiline mode they match not only at the beginning and end of the string, but also at start/end of line.
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## Line start ^
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In the example below the text has multiple lines. The pattern `pattern:/^\d+/gm` takes a number from the beginning of each one:
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```js run
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let str = `1st place: Winnie
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2nd place: Piglet
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33rd place: Eeyore`;
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*!*
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alert( str.match(/^\d+/gm) ); // 1, 2, 33
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*/!*
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```
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Without the flag `pattern:/.../m` only the first number is matched:
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```js run
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let str = `1st place: Winnie
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2nd place: Piglet
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33rd place: Eeyore`;
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*!*
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alert( str.match(/^\d+/g) ); // 1
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*/!*
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```
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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 a line.
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The regular expression engine moves along the text and looks for a string start `pattern:^`, when finds -- continues to match the rest of the pattern `pattern:\d+`.
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## Line end $
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The dollar sign `pattern:$` behaves similarly.
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The regular expression `pattern:\w+$` finds the last word in every line
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```js run
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let str = `1st place: Winnie
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2nd place: Piglet
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33rd place: Eeyore`;
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alert( str.match(/\w+$/gim) ); // Winnie,Piglet,Eeyore
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```
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Without the `pattern:/.../m` flag the dollar `pattern:$` would only match the end of the whole string, so only the very last word would be found.
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## Anchors ^$ versus \n
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To find a newline, we can use not only `pattern:^` and `pattern:$`, but also the newline character `\n`.
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The first difference is that unlike anchors, the character `\n` "consumes" the newline character and adds it to the result.
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For instance, here we use it instead of `pattern:$`:
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```js run
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let str = `1st place: Winnie
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2nd place: Piglet
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33rd place: Eeyore`;
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alert( str.match(/\w+\n/gim) ); // Winnie\n,Piglet\n
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```
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Here every match is a word plus a newline character.
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And one more difference -- the newline `\n` does not match at the string end. That's why `Eeyore` is not found in the example above.
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So, anchors are usually better, they are closer to what we want to get.
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