Using replace and regex to capitalize first letter of each word of a string in JavaScript

Question

The following,though redundant, works perfectly :

'leap of, faith'.replace(/([^ \t]+)/g,"$1");

and prints "leap of, faith", but in the following :

'leap of, faith'.replace(/([^ \t]+)/g,RegExp.$1); it prints "faith faith faith"

As a result when I wish to capitalize each word's first character like:

'leap of, faith'.replace(/([^ \t]+)/g,RegExp.$1.capitalize());

it doesn't work. Neither does,

'leap of, faith'.replace(/([^ \t]+)/g,"$1".capitalize);

because it probably capitalizes "$1" before substituting the group's value.

I want to do this in a single line using prototype's capitalize() method

Answer 1

You can pass a function as the second argument of ".replace()":

"string".replace(/([^ \t]+)/g, function(_, word) { return word.capitalize(); });

The arguments to the function are, first, the whole match, and then the matched groups. In this case there's just one group ("word"). The return value of the function is used as the replacement.