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Lavrentiy Rubtsov 2022-06-07 17:33:09 +06:00 • committed by GitHub
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9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/solution.md
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@ -1,6 +1,6 @@
In order to insert after the `<body>` tag, we must first find it. We can use the regular expression pattern `pattern:<body.*?>` for that.
In this task we don't need to modify the `<body>` tag. We only need to add the text after it.
In this task, we don't need to modify the `<body>` tag. We only need to add the text after it.
Here's how we can do it:
@ -27,10 +27,10 @@ As you can see, there's only lookbehind part in this regexp.
It works like this:
- At every position in the text.
- Check if it's preceded by `pattern:<body.*?>`.
- If it's so then we have the match.
- If it's so, then we have the match.
The tag `pattern:<body.*?>` won't be returned. The result of this regexp is literally an empty string, but it matches only at positions preceeded by `pattern:<body.*?>`.
The tag `pattern:<body.*?>` won't be returned. The result of this regexp is literally an empty string, but it matches only at positions preceded by `pattern:<body.*?>`.
So it replaces the "empty line", preceeded by `pattern:<body.*?>`, with `<h1>Hello</h1>`. That's the insertion after `<body>`.
So it replaces the "empty line", preceded by `pattern:<body.*?>`, with `<h1>Hello</h1>`. That's the insertion after `<body>`.
P.S. Regexp flags, such as `pattern:s` and `pattern:i` can also be useful: `pattern:/<body.*?>/si`. The `pattern:s` flag makes the dot `pattern:.` match a newline character, and `pattern:i` flag makes `pattern:<body>` also match `match:<BODY>` case-insensitively.