How to change this code so that it returns a string instead of an array?

Question

I found myself using a lot of .replace.replace. So I decided to create a function that receives regexes as argument and uses them to replace substrings inside a string. I wanted to return a value, so I decide to use map instead of forEach:

const contents = `"Some text"

<!-- Some comment-->


More text`

const HTMLCommentsRegex = /<!--[\s\S]*?-->/g
const multipleLinesRegex = /\n\n{2,}/g

const regexes = [{
  pattern: HTMLCommentsRegex,
  replacement: ''
}, {
  pattern: multipleLinesRegex,
  replacement: ''
}]

console.log(multiReplace(contents, regexes))

function multiReplace(contents, regexes) {
  const result = regexes.map((regex) => {
    return contents.replace(regex.pattern, regex.replacement)
  })
  return result
}

But I immediately realized my error. I'm returning an array instead of a string (like the original content of contents).

How to modify this code so that the function returns a string instead?

Desired output (basically removing HTML comments and multiple empty lines):

const contents = `"Some text"

More text`

If you always replace it with "", you could create an alternation with | like this: /|\n\n{2,}/ — adiga
– adiga, Commented May 28, 2021 at 5:04
.map() creates a new array from the current one by passing each of the current elements through a mapping function. So, it's a the result is 1:1 with the input. You need a forEach or reduce or a regular loop to get a single result. — VLAZ
– VLAZ, Commented May 28, 2021 at 5:05

CertainPerformance · Accepted Answer · 2021-05-28 05:00:34Z

2

I'd use .reduce instead - on each iteration, carry out the replacement on the accumulator, and return the new replaced string:

const contents = `"Some text"

<!-- Some comment-->


More text`

const HTMLCommentsRegex = /<!--[\s\S]*?-->/g
const multipleLinesRegex = /\n\n{2,}/g

const regexes = [{
  pattern: HTMLCommentsRegex,
  replacement: ''
}, {
  pattern: multipleLinesRegex,
  replacement: ''
}]

const multiReplace = (contents, regexes) => regexes.reduce(
  (str, { pattern, replacement }) => str.replace(pattern, replacement),
  contents
);

console.log(multiReplace(contents, regexes))

answered May 28, 2021 at 5:00

CertainPerformance

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