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I'm maintaining some old code when I reached a headscratcher. I am confused by this regex pattern: /^.*$/ (as supplied as an argument in textFieldValidation(this,'true',/^.*$/,'','').
I interpret this regex as:
So…I think this pattern matches everything, which means the function does nothing but waste processing cycles. Am I correct?
351
The Match-zero-or-more Operator ( * ) This operator repeats the smallest possible preceding regular expression as many times as necessary (including zero) to match the pattern. `*' represents this operator. For example, `o*' matches any string made up of zero or more `o' s.
. means match any character in regular expressions. * means zero or more occurrences of the SINGLE regex preceding it.
Basically (0+1)* mathes any sequence of ones and zeroes. So, in your example (0+1)*1(0+1)* should match any sequence that has 1. It would not match 000 , but it would match 010 , 1 , 111 etc. (0+1) means 0 OR 1. 1* means any number of ones.
The bracketed characters [a-zA-Z0-9] mean that any letter (regardless of case) or digit will match. The * (asterisk) following the brackets indicates that the bracketed characters occur 0 or more times.
It matches a single line of text.
It will fail to match a multiline String, because ^ matches the begining of input, and $ matches the end of input. If there are any new line (\n) or caret return (\r) symbols in between - it fails.
For example, 'foo'.match(/^.*$/) returns foo.
But 'foo\nfoo'.match(/^.*$/) returns null.
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^ "Starting at the beginning.". "Matching anything..."* "0 or more times"$ "To the end of the line."
Yep, you're right on, that matches empty or something.
And a handy little cheat sheet.
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The regexp checks that the string doesn't contain any \n or \r. Dots do not match new-lines.
Examples:
/^.*$/.test(""); // => true
/^.*$/.test("aoeu"); // => true
/^.*$/.test("aoeu\n"); // => false
/^.*$/.test("\n"); // => false
/^.*$/.test("aoeu\nfoo"); // => false
/^.*$/.test("\nfoo"); // => false
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