Javascript selecting part of a string and converting it to uppercase

Question

I have a string like this:

A sampletext
b sampletext3
c exampletext    
A sampletext587
b sampletext5
b sampletextasdf
d sampletext4
b sometext
c sampletextrandom

How do I, in JS, convert all the text on the lines starting with b to upper case?

Thanks!

Answer 1

With regex

"b sampletext3".replace(/^b/gm,function(x){return x.toUpperCase()})
B sampletext3

And assigning it to String Object

String.prototype.toTitleCaseB=function(){
    return this.replace(/^b/gm,function(x){return x.toUpperCase()})
}

Would later use like

"b sampletext3".toTitleCaseB()
B sampletext3

Answer 2

1. split the string on \n
2. loop over the resulting array
3. use substring to extract the first letter and test it
4. optionally set the array item to itself.toUpperCase()
5. join the array