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JavaScript

Can someone explain the logic of "replace(/\w\S*" to me?

Hi all,

I'm doing some JavaScript exercises and i can't seem to wrap my head around this one. The assignment is to "Write a JavaScript function to capitalize the first letter of each word in a string". So far it's pretty clear and i can work my way towards it but the answer provides this piece of code:

function capitalize_Words(str)  
{  
 return str.replace(/\w\S*/g, function(txt){return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();});  
}

I understand the code but i just cannot seem to wrap my head around the /\w\S* part in the replace method. I know a /s "select" whitespace and /g selects each instance but what's the use of "/\w"? And why the \S with a capital and an "*" after it.

If someone could explain this to me....

Thanks!

1 Answer

Josip Dorvak
Josip Dorvak
18,126 Points

The / Is the beginning of a regex (regular expression). The \w looks for all word characters in a string. A word character is a character from a-z, A-Z, 0-9, including the _ (underscore) character. Now the \S is any character that is NOT a whitespace character. You were confusing it with \s(lowercase) which is for whitespace characters. The * is a character that says to look for n zero or more times, where n is the metacharacter(the backslash tokens in the regex) in the regex. Hope this helped a little.

If you need more help go to: http://www.w3schools.com/jsref/jsref_obj_regexp.asp

Exactly what i was looking for. This explains everything i wanted to know!

Thanks :)