正则表达式匹配不需要的字符串

Question

I'm trying to fix an issue with a regex replace statement. This is the code:

var str1 = "bbb/mobile-main.min.js";
var str2 = "ttt/main.min.js";
var str21 = "mobile-main.min.js";
var str22 = "main.min.js";


var re = new RegExp("main\.min\.js" + "(\\?[0-9a-z]+)?", "g");

var ans1 = str1.replace(re, '$1main.78765.min.js');

var ans2 = str2.replace(re, '$1main.78765.min.js');

var ans21 = str21.replace(re, '$1main.78765.min.js');

var ans22 = str22.replace(re, '$1main.78765.min.js');

console.log("ans1: "+ ans1);

console.log("ans2: "+ ans2);

console.log("ans21: "+ ans21);

console.log("ans22: "+ ans22);

The result is:

   "ans1: bbb/mobile-main.78765.min.js"
   "ans2: ttt/main.78765.min.js"
   "ans21: mobile-main.78765.min.js"
   "ans22: main.78765.min.js"

My desired result is only the second string (str2) to match:

"bbb/mobile-main.min.js"

"ttt/main.78765.min.js"

"mobile-main.min.js"

"main.78765.min.js"

Here is a link to jsbin

I couldn't find a regular expression statement to match my goal.. Thanks!

Edit : Jsbin link fixed.

Another limitation: I will not always have something infront of file's name. This should have similar results (only second should match):

mobile-main.min.js

mail.min.js

Edit2 Edited code + JSBin with all conditions

Answer 1

You can use this regex:

var re = new RegExp("(^|/)main\.min\.js" + "(\\?[0-9a-z]+)?", "g");

var ans1 = str1.replace(re, '$1main.78765.min.js'); // bbb/mobile-main.min.js
var ans2 = str2.replace(re, '$1main.78765.min.js'); // ttt/main.78765.min.js

JSBin Demo

(^|/) makes sure that pattern main\\.min\\.js is replaced only when it is at start or preceded by / .