Not sure if I phrase the question correctly so here is an example

let string = "Test text ab/c test
Test t/est
### Test/
Test t/test
Test test"

I'm looking to remove / from only line that contains ### in it so it ends up like this:

Test text ab/c test
Test t/est
### Test
Test t/test
Test test

I assume I can use

mystring.replace(/\/g, '')

But how do I specify that it needs to remove \ only in the line with ###

CodePudding user response：

You can split on newlines and then join them back again.

let string = `Test text ab/c test
Test t/est
### Test/
Test t/test
Test test
Test// ### test / 
`

const parts = string.split("\n")
  .map(s => s.includes("###") ? s.replace(/\//g, '') : s)
  .join("\n");
console.log(parts);

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CodePudding user response：

You can use

string.replace(/(?<=###.*)\/|\/(?=.*###)/g, '')

The (?<=###.*)\/|\/(?=.*###) regex matches a / char that is either preceded with ### and any zero or more non-line break chars, or followed with zero or more non-line break chars and then ###.

See this JavaScript demo:

let string = "Test text ab/c test\nTest t/est\n### /T/e/s/t/\nTest t/test\nTest test"
console.log(string.replace(/(?<=###.*)\/|\/(?=.*###)/g, ''))

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Another solution: split the stirng into lines, then map the resulting array and remove all / chars in the items that includes the ### substring, and then join the string back:

let string = "Test text ab/c test\nTest t/est\n### /T/e/s/t/\nTest t/test\nTest test"
console.log( string.split("\n").map(line => line.indexOf('###') > -1 ? line.replace(/\//g, '') : line).join("\n") )

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CodePudding user response：

.replace() the whole segment then return everything but \/ (the \ is prefixed to / in order to escape it.

const str = `
  Test text ab/c test
  Test t/est
  ### Test/
  Test t/test
  Test test`;

const rgx = /(###. )\//gm;
const sub = `$1`;

console.log(str.replace(rgx, sub));

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