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javascriptregexregex-groupreplaceall

JavaScript replaceAll case-insensitive search using variable rather than a string

I want to do a JavaScript replaceAll() using a variable (rather than a string) in a case-insensitive search, but also retaining the case of the matched text (in the return). For example,

console.log('doc.p:', doc.p.toString().substring(0, 26))
var query = this.manager.store.get('q').value.toString();
console.log('query:', query, '| type:', typeof(query))
console.log(doc.p.toString().replaceAll(/(dna)/gi, '***$1***'))
console.log(doc.p.toString().replaceAll(/(query)/gi, '***$1***'))

is giving

doc.p: DNA deoxyribonucleic acid     // target text
query: dna | type: string            // query text
***DNA*** deoxyribonucleic acid ...  // [success] case-insensitive search; case-sensitive return
DNA deoxyribonucleic acid ...        // [failure] I've also tried (e.g.) $query, $(query), ... here

I was motivated by https://stackoverflow.com/a/19161971/1904943 , and also tried https://stackoverflow.com/a/494046/1904943

Once working, I'll be replacing the '***' (solely for testing / illustration) with HTML code.

Solution

  • Basically, what you want is to create a dynamic regular expression, instead of hardcoding it. This is done with the help of. RegExp constructor, which takes the string representation of a regexp and flags (I messed the string capitalization to demo the preservation of case):

    string1 = 'DnA deoxyribonucleic acid'
string2 = 'DNA deoxyribonucleic aCId'

const replacer = (str, replace) => {
  const re = new RegExp(`(${replace})`, 'gi')
  return str.replaceAll(re, '***$1***')
}

console.log(replacer(string1, 'dna'))
console.log(replacer(string2, 'acid'))