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37 lines
1.0 KiB
XML
37 lines
1.0 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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The caret character <code>^</code> in a regular expression only matches at the beginning of the input, or
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(for multi-line regular expressions) at the beginning of a line. If it is preceded by a pattern
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that must match a non-empty sequence of (non-newline) input characters, it cannot possibly match,
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rendering the entire regular expression unmatchable.
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</p>
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</overview>
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<recommendation>
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<p>
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Examine the regular expression to find and correct any typos.
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</p>
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</recommendation>
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<example>
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<p>
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In the following example, the regular expression <code>/\[^.]*\.css/</code> cannot match any
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string, since it contains a caret assertion preceded by an escape sequence that matches an
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opening bracket.
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</p>
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<sample src="examples/UnmatchableCaret.js" />
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</example>
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<references>
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<li>Mozilla Developer Network: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions">JavaScript Regular Expressions</a>.</li>
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</references>
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</qhelp>
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