How to replace only the pattern not replaced words?

Question

I want to replace the characters while typing in the Textarea. But with the following code snippets (nearly 250 lines are there), here I'm using replace() method of RegEx. It checks against the replacement too. I want it should check only the pattern/regexp.

Test

m -> A //ok
M -> B //ok
, -> F //Wrong, should be C

How can I get hte replacement without changing the order of hte line?

<!DOCTYPE html PUBLIC "-//W3C//Dtd HTML 4.0 transitional//EN">
<html xmlns="http://www.w3.org/1999/xhtml">
   <head>
   <meta charset="UTF-8">
     
   </head>
   <body onload="javascript:formTest.source.focus()">
      <script language="javascript" type="text/javascript">
         var text;
         
         function startConvert()
         {
         text = document.formTest.source.value;  
            
   text = text.replace(/\u006d/g, "A");
   text = text.replace(/M/g, "B");
   text = text.replace(/,/g, "C");
   text = text.replace(/</g, "D");
   text = text.replace(/c/g, "E");
   text = text.replace(/C/g, "F");
   text = text.replace(/v/g, "G");
   text = text.replace(/V/g, "H");
   text = text.replace(/I/g, "I");
   text = text.replace(/x/g, "J");
   text = text.replace(/X/g, "K");
   text = text.replace(/xs/g, "L");
   
   text = text.replace(/\//g, "@");
                    
         document.formTest.destination.value=text;
         }
         
            
      </script>
      <center>
         <table width="500" >
            <tbody>
               <tr>
                  <form name="formTest">
                     <td>        
      <textarea onkeyup="startConvert();" 
      onclick="startConvert();" 
      name="source" 
      rows="5" 
      onselect="startConvert();">
      </textarea>
     
                     </td>
                     <td>
                        <textarea 
      name="destination" rows="5"></textarea>
                     </td>
                  </form>
               </tr>
            </tbody>
         </table>
      </center>
   </body>
</html>

CertainPerformance · Accepted Answer · 2020-03-24T08:50:11.083

2

If a substring from an earlier .replace replaced with something that's being searched for in a later .replace, the result of the earlier .replace will be overwritten by the later one. I'd use an object of replacement values instead, with only a single .replace, so that no character gets checked and replaced more than once.

If the characters to match may be characters with a special meaning in a regex, like [, escape them first:

var text;
const replacements = {
  '\u006d': 'A',
  M: 'B',
  ',': 'C',
  '<': 'D',
  c: 'E',
  C: 'F',
  v: 'G',
  V: 'H',
  I: 'I',
  x: 'J',
  X: 'K',
  xs: 'L',
};
const pattern = new RegExp(
  Object.keys(replacements)
    .map(s => s.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'))
    .join('|'),
  'g'
);
function startConvert() {
  document.formTest.destination.value = document.formTest.source.value
    .replace(pattern, match => replacements[match]);
}

<center>
  <table width="500">
    <tbody>
      <tr>
        <form name="formTest">
          <td>
            <textarea onkeyup="startConvert();" onclick="startConvert();" name="source" rows="5" onselect="startConvert();">
      </textarea>

          </td>
          <td>
            <textarea name="destination" rows="5"></textarea>
          </td>
        </form>
      </tr>
    </tbody>
  </table>
</center>

edited Mar 24 '20 at 08:50

answered Mar 24 '20 at 08:23

CertainPerformance

356,069
52
309
320

Will this method useful to the rest of the lines? – test team Mar 24 '20 at 08:29
What do you mean? It will replace a found character on any line. – CertainPerformance Mar 24 '20 at 08:32
Here, I posted only 13 lines to replace. But there're almost 300 lines to be replaced as this. – test team Mar 24 '20 at 08:35
If you want to be able to transform that into an object quickly, you can use the method I used, with [regex101](https://regex101.com/r/zZuuax/1) – CertainPerformance Mar 24 '20 at 08:37
Thanks, but it isn't work for `text = text.replace(/n\[s/g, "ù--_ü");` and `text = text.replace(/N\[h/g, "ú_ô");` and `text = text.replace(/n\[h/g, "ù--_ô");` – test team Mar 24 '20 at 08:47
If the characters to match may be characters with a special meaning in a regex, like `[`, [escape them first](https://stackoverflow.com/q/3561493) – CertainPerformance Mar 24 '20 at 08:50
Replace the `\w`, which matches only word characters, with anything but a `"`, `[^"]+` – CertainPerformance Mar 24 '20 at 08:55
Thanks, https://pastebin.com/46z0HUiC is the entire list but got errors, please. – test team Mar 24 '20 at 11:06
Add `'` delimiters around the key replacement so that the invalid characters like `\[` are parsed correctly: `'$1': '$2',` – CertainPerformance Mar 24 '20 at 11:07

score 0 · Answer 2 · answered Mar 24 '20 at 08:25

0

Instead of checking against the whole string,

var str = document.formTest.source.value; 
var text = str .substr(str .length - 1);
text = text.replace(/\u006d/g, "A");
...

This will do.

answered Mar 24 '20 at 08:25

David

15,894
22
55
66

What about for multiple characters (string) ? – test team Mar 24 '20 at 08:32
@testteam var text = str .substr(str .length - n); – David Mar 24 '20 at 08:42

score -2 · Answer 3 · answered Mar 24 '20 at 08:23

-2

use onkeyup="functionName()", remove onclick() and onselect()

answered Mar 24 '20 at 08:23

Mohit

80
7

How to replace only the pattern not replaced words?

3 Answers3