Parsing the CSV file contents according to the specified columns

Question

Parsing the CSV file contents according to the specified columns

Currently, I'm involved in a project using AngularJS where I need to extract data from a CSV file column by column using JavaScript. So far, I've successfully retrieved the CSV data and displayed it in the console. While I've managed to separate the data row by row, I'm now seeking guidance on how to achieve this same separation based on columns.

Thank you for your help in advance!

javascript angularjs

Answer 1

Answer №1

CSV can be represented as a two-dimensional array structure. This structure can be manipulated using nested for loops.

For instance:

for(var i = 0; i < columns.length; i++){
   for(var j = 0; j < rows.length; j++){
      matrix[i][j]
   }
}

Answer 2

CSV can be represented as a two-dimensional array structure. This structure can be manipulated using nested for loops.

For instance:

for(var i = 0; i < columns.length; i++){
   for(var j = 0; j < rows.length; j++){
      matrix[i][j]
   }
}

Answer 3

Answer №2

While parsing CSV files may seem straightforward at first glance, it can quickly become complex depending on the source of your CSV data (whether it's user-generated, standardized from an API, etc.):

Dealing with headers
Varying numbers of headers and data columns
Different delimiters (e.g., Germans using ; instead of ,)
Number formatting differences (e.g., Germans using , as decimal separators)
Quoted data that may contain delimiters
Whitespace handling
Different line endings
...

That is why there are numerous CSV parsers available on npm (https://www.npmjs.com/search?q=csv). Some focus on speed like https://www.npmjs.com/package/fast-csv, while others prioritize convenience such as https://www.npmjs.com/package/papaparse.

Most of these parsers return row by row to accommodate processing streams that pass data line by line rather than column by column.

Here is a code snippet to organize your data column-wise:

const input = `header_1,header_2
value 1,value 2
value 3,value 4`

// Separate rows based on known line ending \n
const rows = input.split('\n');

// Extract the header row
const header = rows.shift();

// Determine number of columns by splitting the header using , delimiter
const numberOfColumns = header.split(',').length

// Initialize 2D-array with fixed size
const columnData = [...Array(numberOfColumns)].map(item => new Array());

for(var i=0; i<rows.length; i++) {
  var row = rows[i];
  var rowData = row.split(',');

  // Assuming equal number of columns in header and data rows
  for(var j=0; j<numberOfColumns; j++) {
    columnData[j].push(rowData[j]);
  }
}

console.log("columnData = " + JSON.stringify(columnData, null, 4));

Output will be:

columnData = [
    [
        "value 1",
        "value 3"
    ],
    [
        "value 2",
        "value 4"
    ]
]

Note: This example does not cover tasks such as removing whitespace or converting numerical values.

For easier handling, you can utilize papaparse to parse data row by row and then apply a nested for loop to arrange the data into columns:

const Papa = require('papaparse');

// Example data with ; delimiter and empty lines
const input = `header_1;header_2
1;"2"

3;4`;

// Papaparse options configuration
const parseOptions = {
    quoteChar: '"',
    delimiter: ';',
    skipEmptyLines: true,
    dynamicTyping: true,
}

const parseResult = Papa.parse(input, parseOptions);
const parsedData = parseResult.data;

// Extract the header row
const header = parsedData.shift();

const numberOfColumns = header.length;

// Initialize 2D array with fixed size
const columnData = [...Array(numberOfColumns)].map(item => new Array());

for(var i=0; i<parsedData.length; i++) {
  var rowData = parsedData[i];

  for(var j=0; j<numberOfColumns; j++) {
    columnData[j].push(rowData[j]);
  }
}

console.log("columnData = " + JSON.stringify(columnData, null, 4));

Output will be:

columnData = [
    [
        1,
        3
    ],
    [
        2,
        4
    ]
]

Answer 4

While parsing CSV files may seem straightforward at first glance, it can quickly become complex depending on the source of your CSV data (whether it's user-generated, standardized from an API, etc.):

Dealing with headers
Varying numbers of headers and data columns
Different delimiters (e.g., Germans using ; instead of ,)
Number formatting differences (e.g., Germans using , as decimal separators)
Quoted data that may contain delimiters
Whitespace handling
Different line endings
...

That is why there are numerous CSV parsers available on npm (https://www.npmjs.com/search?q=csv). Some focus on speed like https://www.npmjs.com/package/fast-csv, while others prioritize convenience such as https://www.npmjs.com/package/papaparse.

Most of these parsers return row by row to accommodate processing streams that pass data line by line rather than column by column.

Here is a code snippet to organize your data column-wise:

const input = `header_1,header_2
value 1,value 2
value 3,value 4`

// Separate rows based on known line ending \n
const rows = input.split('\n');

// Extract the header row
const header = rows.shift();

// Determine number of columns by splitting the header using , delimiter
const numberOfColumns = header.split(',').length

// Initialize 2D-array with fixed size
const columnData = [...Array(numberOfColumns)].map(item => new Array());

for(var i=0; i<rows.length; i++) {
  var row = rows[i];
  var rowData = row.split(',');

  // Assuming equal number of columns in header and data rows
  for(var j=0; j<numberOfColumns; j++) {
    columnData[j].push(rowData[j]);
  }
}

console.log("columnData = " + JSON.stringify(columnData, null, 4));

Output will be:

columnData = [
    [
        "value 1",
        "value 3"
    ],
    [
        "value 2",
        "value 4"
    ]
]

Note: This example does not cover tasks such as removing whitespace or converting numerical values.

For easier handling, you can utilize papaparse to parse data row by row and then apply a nested for loop to arrange the data into columns:

const Papa = require('papaparse');

// Example data with ; delimiter and empty lines
const input = `header_1;header_2
1;"2"

3;4`;

// Papaparse options configuration
const parseOptions = {
    quoteChar: '"',
    delimiter: ';',
    skipEmptyLines: true,
    dynamicTyping: true,
}

const parseResult = Papa.parse(input, parseOptions);
const parsedData = parseResult.data;

// Extract the header row
const header = parsedData.shift();

const numberOfColumns = header.length;

// Initialize 2D array with fixed size
const columnData = [...Array(numberOfColumns)].map(item => new Array());

for(var i=0; i<parsedData.length; i++) {
  var rowData = parsedData[i];

  for(var j=0; j<numberOfColumns; j++) {
    columnData[j].push(rowData[j]);
  }
}

console.log("columnData = " + JSON.stringify(columnData, null, 4));

Output will be:

columnData = [
    [
        1,
        3
    ],
    [
        2,
        4
    ]
]

Parsing the CSV file contents according to the specified columns

Answer №1

Answer №2

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