使用正则表达式从字符串中提取特定字符

Question

I need to split an email address and take out the first character and the first character after the '@'

I can do this as follows:

'bar@foo'.split('@').map(function(a){ return a.charAt(0); }).join('')
--> bf

Now I was wondering if it can be done using a regex match, something like this

'bar@foo'.match(/^(\w).*?@(\w)/).join('')
--> bar@fbf

Not really what I want, but I'm sure I miss something here! Any suggestions ?

Answer 1

If I understand correctly, you are quite close. Just don't join everything returned by match because the first element is the entire matched string.

'bar@foo'.match(/^(\w).*?@(\w)/).splice(1).join('')
--> bf

Answer 2

Why use a regex for this? just use indexOf to get the char at any given position:

var addr = 'foo@bar';
console.log(addr[0], addr[addr.indexOf('@')+1])

To ensure your code works on all browsers, you might want to use charAt instead of [] :

console.log(addr.charAt(0), addr.charAt(addr.indexOf('@')+1));

Either way, It'll work just fine, and This is undeniably the fastest approach
If you are going to persist, and choose a regex, then you should realize that the match method returns an array containing 3 strings, in your case:

/^(\w).*?@(\w)/
["the whole match",//start of string + first char + .*?@ + first string after @
 "groupw 1 \w",//first char
 "group 2 \w"//first char after @
]

So addr.match(/^(\\w).*?@(\\w)/).slice(1).join('') is probably what you want.

Answer 3

Using regex:

matched="",
'abc@xyz'.replace(/(?:^|@)(\w)/g, function($0, $1) { matched += $1; return $0; });

console.log(matched);
// ax

Answer 4

The regex match function returns an array of all matches, where the first one is the 'full text' of the match, followed by every sub-group. In your case, it returns this:

bar@f
b
f

To get rid of the first item (the full match), use slice :

'bar@foo'.match(/^(\w).*?@(\w)/).slice(1).join('\r')

Answer 5

使用String.prototype.replace和正则表达式 ：

'bar@foo'.replace(/^(\w).*@(\w).*$/, '$1$2');  // "bf"

Answer 6

Or using RegEx

^([a-zA-Z0-9])[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@([a-zA-Z0-9-])[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$

Fiddle