无法使用RegEx将索引值放在方括号内

Question

There are two strings. I'm trying to put index value inside empty brackets:

var capacity = 'room[price_group_ids][][capacity]';
var group = 'room[price_group_ids][][group][%s][]';

For example, If an index is 1, they should be:

var capacity = 'room[price_group_ids][1][capacity]';
var group = 'room[price_group_ids][1][group][%s][]';

And if the index is 2, they should look like as the following:

var capacity = 'room[price_group_ids][2][capacity]';
var group = 'room[price_group_ids][2][group][%s][]';

What I've tried and it gives unexpected result:

var index = 2;

var capacity = 'room[price_group_ids][][capacity]'.replace(/\[(.+?)\]/g, "[" + index +"]"); // Should become room[price_group_ids][2][capacity]
var group = 'room[price_group_ids][][group][%s][]'.replace(/\[(.+?)\]/g, "[" + index +"]"); // Should become room[price_group_ids][2][group][%s][]

I'm not good at RegEx and looking for an advice on how to resolve that

Answer 1

A simple replace should work here.

This will only replace the first occurrence of [] , so you don't have to worry about others. g flag is used to replace globally ie all the occurrences of the specified value

capacity.replace('[]', `[${index}]`);

 var index = 2; var capacity = 'room[price_group_ids][][capacity]'; var group = 'room[price_group_ids][][group][%s][]'; capacity = capacity.replace('[]', `[${index}]`); group = group.replace('[]', `[${index}]`); console.log(capacity) console.log(group) 

Answer 2

Since you want to match first occurrence of [] so don't use g flag. Also no need to match anything else (.+?) , just /\\[\\]/ is enough.

Another way is to simply replace string [] with [1]

 let index = 2 console.log('room[price_group_ids][][capacity]'.replace(/\\[\\]/, `[${index}]`)); console.log('room[price_group_ids][][group][%s][]'.replace(/\\[\\]/, `[${index}]`)); 

Answer 3

The reg exp /\\[(.+?)\\]/g matches 1-or-more of anything between [] brackets. You want to detect [ and ] right next to each other; simply:

/\[\]/

Also, you want to ditch the g at the end, unless you want the replacement to occur for all occurrences of [] -- the g means global .

But there are non-regex approaches, too, as shown in the other answers.