Parse dot notation columns into nested objects #414

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1. jivung

   added

   enhancement

   on Jan 24, 2024
2. wdavidw commented on Jan 24, 2024

   

   wdavidw

   on Jan 24, 2024

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   The closest thing is the column option but it doesnt support (yet?) nested column.
3. datu925 commented on Jan 31, 2024

   

   datu925

   on Jan 31, 2024

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   +1 to this, this would be a great feature.

   In the archived repo, this was requested here: adaltas/node-csv-parse#76.

   And I came here to make a similar suggestion. I'm rolling my own simple version right now but if this was part of the library, even better.

   I think the argument for it is that csv-stringify offers this nested properties behavior when outputting, so being able to read that format when parsing (enabling a "round trip") is desirable.
4. wdavidw commented on Jan 31, 2024

   

   wdavidw

   on Jan 31, 2024

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   Yes, I remember a few years back porting the underscore code into the library to support this feature without including an external dependency. A little buzy in the next copple of weeks between work and then holidays but I'll try to find the time.

   👍React with 👍2Reacted by Michael Jivung and Dan Turcza
5. datu925 commented on Apr 17, 2024

   

   datu925

   on Apr 17, 2024

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   In case it helps as a starting point, my implementation was something like the below (I've edited it a bit to remove project-specific things, so it may no longer compile). NestedKeyVal was a custom type that is supposed to represent a possibly nested string-keyed object.

   export function flatToNested(
     rows: any[],
   )  {
     const outputs: NestedKeyVal[] = [];
     for (const row of rows) {
       const output: NestedKeyVal = {};
       for (const columnName in row) {
         let val = row[columnName];
   
         const chunks = columnName.split('.');
         // dest is basically a pointer to a particular object or subobject in
         // the output structure. It starts at the root output for each key but
         // advances into sub-objects to allow nesting.
         let dest = output;
         if (chunks.length === 1) {
           dest[chunks[0]] = val;
         } else {
           for (const chunk of chunks.slice(0, -1)) {
             if (!(chunk in dest)) {
               const subobj: NestedKeyVal = {};
               dest[chunk] = subobj;
             }
             dest = dest[chunk];
           }
           dest[chunks.at(-1)!] = val;
         }
       }
       outputs.push(output);
     }
     return outputs;
   }