A pattern matching formula to eliminate specific characters from the beginning to the end of a string

I am facing an issue with extracting content from a given string:

var string = "From: Sarah<br />
 Sent: 10 May 2021 09:45:20</br />
 To: Alice<br />
 Subject: Meeting Reminder<br /><br />

 Hi Alice, 
<br />
Here is a reminder about our meeting tomorrow. 
<br />
See you then! 
<br />
Sarah"

I need to extract the email body content starting from the line after the "Subject" line in the given string.

My current approach involves using the substring method like this:

string.substring(string.lastIndexOf('Subject'), string.length - 1)

However, this approach also includes the "Subject" line in the extracted content which is not desirable. Is there any regex library or alternative method that can help me achieve the desired result?

javascriptregexsubstringsplice

Answer №1

To utilize the string.replace method, you can implement the following:

var message = string.replace(/^[\s\S]*\s+Subject: [^\n]*\n+/, '')

Implementation:

var string = `From: Jenna<br />
Sent: 18 May 2021 09:45:21</br />
To: Alex<br />
Subject: Test email content<br /><br />

Hi Alex,
<br />
This email is to test the emailing system.
<br />
Thank you,
<br />
Jenna`

var body = string.replace(/^[\s\S]*\s+Subject: [^\n]*\n+/, '')

document.writeln("<pre>" + body + "</pre>")

The pattern [\s\S]* matches zero or more of any characters, including newline. It then removes the line containing "Subject:".

Result:

"Hi Alex,
<br />
This email is to test the emailing system.
<br />
Thank you,
<br />
Jenna"

Answer №2

While others may offer a non-regex solution, here is one that uses regex

[\s\S]*Subject\s*:.*([\s\S]+) <-- the desired result will be in the first capturing group

Check out the Regex Demo here

See it in action with this JavaScript demo

var re = /[\s\S]*Subject\s*:.*([\s\S]+)/gm; 
var str = `From: Jeremy<br />
Sent: 22 Apr 2016 12:08:03</br />
To: Mark<br />
Subject: Another test email<br /><br />

Hi Mark, 
<br />
I'm sending this email as a way to test the email! 
<br />
Cheers, 
<br />
Jeremy`
var m = re.exec(str);
document.writeln("<pre>" + m[1] + "</pre>");

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