regular expression for double slash in javascript

Question

I am quite new to regular expression and I want that in my regular expression it should accept only \\ (double back slash ) and not \ (single back slash).

         isFilePathValid: function (get) {
           var forbiddenCharactersRegexp = /[<>|?*]/,
               directorySeparatorsRegexp = /[/\\]/,
              directorySeparatorsRegexp1 = /[\\{2}]/,
              filePath = get('filePath').trim();

        return directorySeparatorsRegexp.test(filePath)
            && 
       !directorySeparatorsRegexp.test(filePath.charAt(filePath.length - 1))
            && !forbiddenCharactersRegexp.test(filePath) && 
        directorySeparatorsRegexp1.test(filePath) ;
    }

the correct file paths are 1. \\abc 2. C:\abd 3. C:\abd\abc

Could you be more specific on this? Should the regex accept only two backslashes? Should it accept the backslashes amongst other characters or just on their own? Should it accept more than just 1 pair of backslashes or just the one? Provide example test cases, highlighting what would pass and what wouldn't. — George
– George, Commented Jun 22, 2017 at 9:41

cнŝdk · Accepted Answer · 2017-06-22 10:07:14Z

2

You need to make sure you have two occurences using {2}, this is the Regex you need:

/\\{2}/g

This is a Regex demo.

Edit:

Make sure you escape the \ as \\ in your string because the string parser in your program will remove one of them when "de-escaping" it for the string, you can check the discussion her and that's why it didn't work in your case.

This is a Demo snippet:

const regex = /\\{2}/g;
const str = `A sample text \\\\ that has nothing\\ on it.`;
let m;

while ((m = regex.exec(str)) !== null) {
  // This is necessary to avoid infinite loops with zero-width matches
  if (m.index === regex.lastIndex) {
    regex.lastIndex++;
  }

  // The result can be accessed through the `m`-variable.
  m.forEach((match, groupIndex) => {
    console.log(`Found match, group ${groupIndex}: ${match}`);
  });
}

Note the escaped \\\\ in the Demo string.

edited Jun 22, 2017 at 10:07

answered Jun 22, 2017 at 9:41

cнŝdk

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1 Comment

abc31 Over a year ago

this is my code isFilePathValid: function (get) { var forbiddenCharactersRegexp = /[<>|?*]/, directorySeparatorsRegexp = /[/\]/, filePath = get('filePath').trim(); return directorySeparatorsRegexp.test(filePath) && !directorySeparatorsRegexp.test(filePath.charAt(filePath.length - 1)) && !forbiddenCharactersRegexp.test(filePath); }

Mr.Pandya · Accepted Answer · 2017-06-22 10:14:30Z

0

Try with following regular exprsssion

^^(\\\\){1}$

edited Jun 22, 2017 at 10:14

answered Jun 22, 2017 at 9:36

Mr.Pandya

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3 Comments

pwolaq Over a year ago

this will accept \\, \\\\, and any other multiple of 2

Mr.Pandya Over a year ago

You need only double

Mr.Pandya Over a year ago

try this ^(\\\\){1}$

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