正则表达式javascript不返回括号

Question

When I am trying to do my regex in js:

 var matc = source.match(/sometext(\\d+)/g); 

The result I get is "sometext5615", "sometext5616"...etc But what I want: is to get "5615", "5616"...etc

Do you have any idea how to get only what is inside the parenthese ?

Answer 1

String.prototype.match has two different behaviors:

• If the regex doesn't have the global g flag, it returns regex.exec(str) . That means that, if there is a match, you will get an array where the 0 key is the match, the key 1 is the first capture group, the 2 key is the second capture group, and so on.

• If the regex has the global g flag, it returns am array with all matches, but without the capturing groups.

Therefore, if you didn't use the global flag g , you could use the following to get the first capture group

var matc = (source.match(/sometext(\d+)/) || [])[1];

However, since you use the global flag, you must iterate all matches manually:

var rg = /sometext(\d+)/g,
    match;
while(match = rg.exec(source)) {
    match[1]; // Do something with it, e.g. push it to an array
}

Answer 2

JavaScript does not have a "match all" for global matches, so you cannot use g in this context and also have capture groups. The simplest solution would be to remove the g and then just use matc[1] to get 5615, etc.

If you need to match multiple of these within the same string then your best bet would be to do a "search and don't replace"

var matc = [];
source.replace(/sometext(\d+)/g, function (_, num) {
    matc.push(num);
});