Enhance regex performance using tokens

Currently, I am using this regex pattern which is functional, but there is room for optimization. The pattern seems very "literal" and may be impacting the processing speed when using tokens. While it could potentially run faster with optimized tokens, the process is not very straightforward for beginners...

const pattern = /left\s:([-]{0,1}[0-9]{1,4})px;\stop:([0-9]{1,4})px;"\s\s\tonmouseover="updi\(event,'([0-9]{4}-[0-9]{2}-[0-9]{2})\s([0-9]{2}:[0-9]{2})\s([A-Z]{3,4})\s\((T[+]{1}\s[0-9]{1}:[0-9]{2}|T[+]{1}[0-9]{2,3}:[0-9]{2})\)<br>Distances:&nbsp;([0-9]{1,4}\.[0-9]{1}nm)\/([0-9]{1,4}\.[0-9]{1}nm)<br><b>Wind:</b>\s([0-9]{1,3}&deg);\s([0-9]{1,2}\.[0-9]{1}\skt)\s\(<b>TWA\s([-]{0,1}[0-9]{1,3}&deg);</b><br><b>Heading:</b>\s([0-9]{1,3}&deg);<b>Sail:</b>\s([a-zA-Z]{2,4})<br><b>Boat\sSpeed:</b>\s([0-9]{1,3}\.[0-9]{2}\skts)/

The regex pattern extracts values that can be utilized later in the code, as shown in the following example:

<img src="img/dot.png" alt="" class="abs" style="z-index: 1; left :-4904px; top:2437px;" 
onmouseover="updi(event,'2019-10-15 02:00 CEST (T+ 1:50)<br>Distances:&nbsp;1271.8nm/447.1nm<br><b>Wind:</b> 295&deg; 5.8 kt (<b>TWA 65&deg;</b>)<br><b>Heading:</b> 230&deg;<b>Sail:</b> Jib<br><b>Boat Speed:</b> 3.23 kts','220px')" onmouseout="cleari()" 
onmousedown="show_wind(366);">
<img src="img/dot.png" alt="" class="abs" style="z-index: 1; left :49px; top:243px;" 
onmouseover="updi(event,'2019-10-15 02:00 CET (T+363:50)<br>Distances:&nbsp;1271.8nm/447.1nm<br><b>Wind:</b> 295&deg; 5.8 kt (<b>TWA 65&deg;</b>)<br><b>Heading:</b> 230&deg;<b>Sail:</b> Jib<br><b>Boat Speed:</b> 3.23 kts','220px')" onmouseout="cleari()" 
onmousedown="show_wind(366);">
javascriptregex

Answer №1

Using an HTML parser is a much better approach for solving this issue. If there are even slight differences between your regex and the HTML structure, everything could potentially break. It's not advisable to work with HTML using Regex.

However, if you still prefer optimizing your regex, it can be refined as follows:

  • [0-9] can be replaced with \d
  • [a-zA-Z_] can be replaced with \w
  • [-]{0,1} can be replaced with -?
  • T[+]{1} can be replaced with T\+
  • If text is unimportant, it can often be skipped using .*, provided there is a clear pattern after it

Below is a simplified version of the regex you shared. It may not necessarily be faster than the original one since the provided regex doesn't seem to function correctly. I strongly suggest utilizing an HTML parser instead of relying solely on regex.

left :(-?\d{1,4})px; top:(-?\d{1,4})px;"\s*onmouseover="updi\(event,'(\d{4}-\d{2}-\d{2}) (\d{2}:\d{2}) (\w{3,4}) \((T\+ ?\d{1,3}:\d{2})\)<br>Distances:&nbsp;(\d{1,4}\.\dnm)\/(\d{1,4}\.\dnm)<br><b>Wind:<\/b> (\d{1,3}&deg); (\d{1,2}\.\d kt) \(<b>TWA (-?\d{1,3}&deg);<\/b>\)<br><b>Heading:<\/b> (\d{1,3}&deg);<b>Sail:<\/b> (\w{2,4})<br><b>Boat Speed:<\/b> (\d{1,3}\.\d{2} kts)

Test it here!

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