Javascript - How To Use Regex Process The Following Complicated String

I have the following string that will occur repeatedly in a larger string: [SM_g]word[SM_h].[SM_l] " Notice in this string after the phrase '[SM_g]word[Sm_h]' there are th

Solution 1:

You need to put each component within an alternation in a grouping construct with maximum match try of 3 if it is necessary:

\[SM_g]word(\[SM_h])((?:\.|\[SM_l]| ?"){0,3})

You may replace word with .*? if it is not a constant or specific keyword.

Then in replacement string you should do:

$1$3$2

var re = /(\[SM_g]word)(\[SM_h])((?:\.|\[SM_l]| ?"){0,3})/g;
var str = `[SM_g]word[SM_h][SM_l] ".`;

console.log(str.replace(re, `$1$3$2`));

Solution 2:

This seems applicable for your process, in other word, changing sub-string position.

(\[SM_g])([^[]*)(\[SM_h])((?=([,\.])|(\[SM_l])|( ?&\\?quot;)).*)?

Demo,,, in which all sub-strings are captured to each capture group respectively for your post processing.

[SM_g] is captured to group1, word to group2, [SM_h] to group3, and string of all trailing part is to group4, [,\.] to group5, [SM_l] to group6, " ?&\\?quot;" to group7.

Thus, group1~3 are core part, group4 is trailing part for checking if trailing part exists, and group5~7 are sub-parts of group4 for your post processing.

Therefore, you can get easily matched string's position changed output string in the order of what you want by replacing with captured groups like follows.

\1\2\7\3or $1$2$7$3  etc..

For replacing in Javascript, please refer to this post. JS Regex, how to replace the captured groups only?

But above regex is not sufficiently precise because it may allow any repeatitions of the sub-part of the trailing string, for example, \1\2\3\5\5\5\5 or \1\2\3\6\7\7\7\7\5\5\5, etc..

To avoid this situation, it needs to adopt condition which accepts only the possible combinations of the sub-parts of the trailing string. Please refer to this example. https://regex101.com/r/6aM4Pv/1/ for the possible combinations in the order.

But if the regex adopts the condition of allowing only possible combinations, the regex will be more complicated so I leave the above simplified regex to help you understand about it. Thank you:-)