CODEWITHSUNDEEP
javascriptjqueryarraysalgorithmcsv
Liam Johnson
Liam Johnson

Reputation: 1

How to Approach Parsing CSV in Javascript

(My first post, I apologise for any mistakes)

I'm working with a small set of data in CSV files, which I need to read, process, and then export as a text file.

The format of the CSV data is:

REGO,STATUS,SHIFT,LOCATION,LOADED
CCA4110,StatusON,5:43,Brisbane,1
CCA4112,StatusON,5:44,Syndey,0
CCA4118,StatusON,6:11,Melbourne,1

I want to be able to take each line after the header row, and check

a) if the 'LOADED' value equals 0 or 1 (skip to next row if 1).

b) If 'LOADED' is 0, then check if the 'REGO' value matches a pre-defined list of 'REGO' values.

c) If a match, change the 'SHIFT' time.

d) If no match, move on to next row.

After that, I want to export all of the rows, with only the 'REGO' and 'SHIFT' values, to look like:

CCA4110,5:43
CCA4112,5:33
...

Because this feels a little complex to me, I'm having trouble visualising the best way to approach this problem. I was wondering if someone could help me think about this in a way that isn't just hacking together a dozen nested for loops.

Thanks very much,

Liam

Edit: a question about checking multiple conditions:

Say I have two CSV files:

List_to_Change.csv

REGO,STATUS,SHIFT,LOCATION,LOADED       
CCA2420,StatusOn,11:24,BRISBANE,1
CCA2744,StatusOn,4:00,SYDNEY,1
CCA2009,StatusOn,4:00,MELBOURNE,0

List_to_Compare.csv

REGO,CORRECT_SHIFT
CCA2420,6:00
CCA2660,6:00
CCA2009,5:30

An algorithm:

1. Check value in 'List_to_Check.csv' 'LOADED' column

A. If value equals '0' go to step 2.

B. If value equals '1' skip this row and go to next.

2. Check if 'REGO' value in 'List_to_Check.csv' shows up in 'List_to_Compare.csv'

A. If true go to step 3.

B. If false skip this row and go to next.

3. Change 'SHIFT' value in 'List_to_Change.csv' with value shown in 'List_to_Compare.csv'

4. Stringify each row that was changed and export to text file.

Upvotes: 0

Views: 130

Answers (1)

user3297291
user3297291

Reputation: 23372

My advice would be to split the work flow in to three steps:

  1. Parse all rows to javascript objects
  2. Perform the logic on the array of objects
  3. Stringify the objects back to CSV

// This creates an object based on an order of columns:
const Entry = ([rego, status, shift, location, loaded]) =>
  ({ rego, status, shift, location, loaded });
  
// Which entries are we interested in?
const shouldHandleEntry = ({ loaded }) => loaded === "1";

// How do we update those entries?
const updateEntry = entry => ({
  ...entry,
  shift: ["CCA4118"].includes(entry.rego)
    ? "5:33"
    : entry.shift
});

// What do we export?
const exportEntry = ({ rego, shift }) => `${rego},${shift}`;

// Chain the steps to create a new table:
console.log(
  csvBody(getCSV())
    .map(Entry)
    .filter(shouldHandleEntry)
    .map(updateEntry)
    .map(exportEntry)
    .join("\n")
)


// (This needs work if you're using it for production code)
function csvBody(csvString) {
  return csvString
    .split("\n")
    .map(line => line.trim().split(","))
    .slice(1);
};

function getCSV() { return `REGO,STATUS,SHIFT,LOCATION,LOADED
CCA4110,StatusON,5:43,Brisbane,1
CCA4112,StatusON,5:44,Sydney,0
CCA4118,StatusON,6:11,Melbourne,1`; }

Upvotes: 2

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