Question 162160 in Javascript Question posted in
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Can Javascript Regexp match when only one occurence is found?

For example, I want to check if a file has only one extension. I tried to use the groups, but they don’t allow me to verify that they appear only once (I didn’t find out how to do it)

Here is an example used:

.(js|jsx)$

For example, if js and jsx are allowed:

test.js -> should match
test.jsx -> should match
test.ts -> should not match
test.js.jsx -> should not match

Any string with .js.jsx, .jsx.jsx, .jsx.js or .js.js at the end are not allowed.

Tags:

2

Answers


  1. 0

    .w+.w+ this regex expression matches files with more than one extension. However, it may be necessary to do some string operations first.

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  2. 0

    Only one extension, means no dot before the extension, use [^.] to specify any chars but not dot. The full regular expression:

    /^[^.]+.(js|jsx)$/

    But if you want to check if a file has only one allowed extension, you can use a global match:

    /.(js|jsx)b/g

    Here is a example:

    const REGEXP1 = /.(js|jsx)b/g;
const REGEXP2 = /^[^.]+.(js|jsx)$/;

const files = [
  'test.js',
  'test.jsx',
  'test.ts',
  'test.js.jsx',
  'test.ts.jsx',
];

console.log('REGEXP1');

files.forEach((file) => {
  const match = file.match(REGEXP1);
  console.log(!!(match && match.length === 1));
});

console.log('REGEXP2');

files.forEach((file) => {
  const match = file.match(REGEXP2);
  console.log(!!match);
});
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