Why is $1 in replace not doing its job?

Question

JavaScript

Task: to make an automatic insertion of a drop cap in the visual editor.
Solution methods: through replace.
Tell me what's wrong here? O_o

Here is the code on jsfiddle.com

Answer 1

\s this

[ \f\n\r\t\v​\u00a0\u1680​\u180e\u2000​-\u200a​\u2028\u2029\u202f\u205f​\u3000\ufeff]

\u200Bit does not include
/<br>[\s\u200B]*([^<])/gworks

Answer 2

line 12 /\<br\>\s*([^<])/gwithout quotes