JS Regex for matching specific array increment ignoring string and seperate increment

Question

I have the following input fields with name attributes of:

carousels['components'][0][0][title]
carousels['components'][0][1][title]
carousels['components'][0][2][title]

carousels['components'][1][0][title]
carousels['components'][1][1][title]
carousels['components'][1][2][title]

carousels['components'][2][0][title]
carousels['components'][2][1][title]
carousels['components'][2][2][title]

I am trying to match the final [ number ] eg this part:

carousels['components'][2][THIS][title]
carousels['components'][2][THIS][title]
carousels['components'][2][THIS][title]

While ignoring the rest

Here is my regex pattern:

/(\[[^components\]])+(\[*])/

This affects both of the int's within brackets when I just want the last one. This regex also doesn't recognize the specific requirement of the first array key 'component'

Live regex test here:

http://www.regexpal.com/?fam=94974

Answer 1

If you want to get the last [ + digits + ], you can use

/^.*\[(\d+)\].*$/

See the regex demo

Backtracking will help getting exactly the last occurrence of [digits]. Grab Group 1 value.

var re = /^.*\[(\d+)\].*$/; 
var str = 'carousels[\'components\'][0][0][title]\ncarousels[\'components\'][0][1][title]\ncarousels[\'components\'][0][2][title]\n\ncarousels[\'components\'][1][0][title]\ncarousels[\'components\'][1][1][title]\ncarousels[\'components\'][1][2][title]\n\ncarousels[\'components\'][2][0][title]\ncarousels[\'components\'][2][1][title]\ncarousels[\'components\'][2][2][title]';

for (var s of str.split("\n")) {
    var res = (m=re.exec(s)) ? m[1] : "";
    if (res) {
      document.body.innerHTML += s + ": " + res + "<br/>";
    }
}

UPDATE:

To get the first [ + digits + ], you need to use lazy matching with the first dot:

/^.*?\[(\d+)\].*$/
    ^ - Here, the ? will make matching lazy/reluctant 
        (it will match any 0+ chars other than a newline as few as possible)

See another regex demo.