RegExp match and replace to it's uppercase in javascript-CodePudding

I have a sentence with a colon in the middle, and want to capitalize the first word after the colon, I would like to know how to replace the matching letter with its' upper case using regexp in javascript, however xx.replace(/(:\s\w)/, '$1'.toUpperCase()) doesn't work, it returns Lactobacillus strains: a BIOPEP-UWM database-based analysis. Expect Lactobacillus strains: A BIOPEP-UWM database-based analysis.

MWE:

var xx = 'Lactobacillus strains: a BIOPEP-UWM database-based analysis';
xx.replace(/(:\s\w)/, '$1'.toUpperCase());

Any suggestion is appreciated.

CodePudding user response：

All you need to do is use a callback function as the second argument instead of '$1'

var xx = 'Lactobacillus strains: a BIOPEP-UWM database-based analysis';
console.log(xx.replace(/:\s\w/, fullMatch => fullMatch.toUpperCase()));

What you were doing was capitalizing the literal value '$1', which is the same, so it was just passing '$1' into the replace function

CodePudding user response：

The following regex ... /(?<=:\s*)\p{Ll}/gu ... matches exactly just any lowercase letter which follows a colon and an optional whitespace (sequence). It does so by using the unicode property escape for a lowercase letter ... \p{Ll} ... and by utilizing a positive lookbehind.

const sampleText =
`Lactobacillus strains: a BIOPEP-UWM database-based analysis
Lactobacillus strains  :another BIOPEP-UWM database-based analysis
Lactobacillus strains   :   a   BIOPEP-UWM database-based analysis
Lactobacillus strains:another BIOPEP-UWM database-based analysis
Lactobacillus strains:Another BIOPEP-UWM database-based analysis`;

// see ... [https://regex101.com/r/dXfa2j/1]
const regXLowerCaseAfterColon = /(?<=:\s*)\p{Ll}/gu;

console.log(
  sampleText
    .replace(regXLowerCaseAfterColon, match => match.toUpperCase())
);

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