How do you delete every line inside of a string that doesn’t contain a specific word?

There’s a string with multiple lines of random characters, I’d like to delete every line that doesn’t contain the word

:tesTWORD:

For example, this part of the original string

"111"1"13648""
PA4123:tesTWORD:a6b4ba21ba54f6bde411930bd864b700"""""
"101"1"00000368""
PA1239:tesTWORD:a6b4ba21ba54f6bde411930b0001cb9d"""
PA0545:tesTWOR:b598944d1ba4c787e411800b8043559c""
""
PA1238:tesTWORD:a6b4ba21ba54f6bde411920b6ba5f90b
PA0545:tesWOR:b598944d1ba4c787e411800b8043559c""
3646475

Would turn into this:

PA4123:tesTWORD:a6b4ba21ba54f6bde411930bd864b700"""""
PA1239:tesTWORD:a6b4ba21ba54f6bde411930b0001cb9d"""
PA1238:tesTWORD:a6b4ba21ba54f6bde411920b6ba5f90b

So basically all lines that don’t contain the exact word :tesTWORD: get deleted.

I have tried a bunch of different things like playing around with arrays, but nothing worked like it’s supposed to

Answer

You can use n to split it into an array,then filter the array,finally using join() to form a new string

str.split('n').filter(d => d.indexOf(':tesTWORD:') > -1).join('n')

let str = `"111"1"13648""
PA4123:tesTWORD:a6b4ba21ba54f6bde411930bd864b700"""""
"101"1"00000368""
PA1239:tesTWORD:a6b4ba21ba54f6bde411930b0001cb9d"""
PA0545:tesTWOR:b598944d1ba4c787e411800b8043559c""
""
PA1238:tesTWORD:a6b4ba21ba54f6bde411920b6ba5f90b
PA0545:tesWOR:b598944d1ba4c787e411800b8043559c""
3646475`

let result = str.split('n').filter(d => d.indexOf(':tesTWORD:') > -1).join('n')

console.log(result)