When dealing with CSV (Comma-Separated Values) strings in JavaScript, parsing can be challenging when data can contain commas within quoted fields. Here's how you can effectively handle this scenario with a detailed solution:
To ensure the input string is a valid CSV string, we define a validation regex:
re_valid = r"""
# Validate a CSV string having single, double or un-quoted values.
^ # Anchor to start of string.
\s* # Allow whitespace before value.
(?: # Group for value alternatives.
'[^'\]*(?:\[\S\s][^'\]*)*' # Either Single quoted string,
| "[^"\]*(?:\[\S\s][^"\]*)*" # or Double quoted string,
| [^,'"\s\]*(?:\s+[^,'"\s\]+)* # or Non-comma, non-quote stuff.
) # End group of value alternatives.
\s* # Allow whitespace after value.
(?: # Zero or more additional values
, # Values separated by a comma.
\s* # Allow whitespace before value.
(?: # Group for value alternatives.
'[^'\]*(?:\[\S\s][^'\]*)*' # Either Single quoted string,
| "[^"\]*(?:\[\S\s][^"\]*)*" # or Double quoted string,
| [^,'"\s\]*(?:\s+[^,'"\s\]+)* # or Non-comma, non-quote stuff.
) # End group of value alternatives.
\s* # Allow whitespace after value.
)* # Zero or more additional values
$ # Anchor to end of string.
"""To parse individual values from the validated CSV string, we utilize the following regex:
re_value = r""" # Match one value in valid CSV string. (?!\s*$) # Don't match empty last value. \s* # Strip whitespace before value. (?: # Group for value alternatives. '([^'\]*(?:\[\S\s][^'\]*)*)' # Either : Single quoted string, | "([^"\]*(?:\[\S\s][^"\]*)*)" # or : Double quoted string, | ([^,'"\s\]*(?:\s+[^,'"\s\]+)*) # or : Non-comma, non-quote stuff. ) # End group of value alternatives. \s* # Strip whitespace after value. (?:,|$) # Field ends on comma or EOS. """
With these regexes defined, we can implement a function to parse the CSV string:
function CSVtoArray(text) {
// Return NULL if input string is not well formed CSV string.
if (!re_valid.test(text)) return null;
var a = []; // Initialize array to receive values.
text.replace(re_value, // "Walk" the string using replace with callback.
function(m0, m1, m2, m3) {
// Remove backslash from \' in single quoted values.
if (m1 !== undefined) a.push(m1.replace(/\'/g, "'"));
// Remove backslash from \" in double quoted values.
else if (m2 !== undefined) a.push(m2.replace(/\"/g, '"'));
else if (m3 !== undefined) a.push(m3);
return ''; // Return empty string.
});
// Handle special case of empty last value.
if (/,\s*$/.test(text)) a.push('');
return a;
}Here are some examples of input CSV strings and their corresponding parsed outputs:
// Test string from original question
let result = CSVtoArray("'string, duppi, du', 23, lala");
console.log(result); // ['string, duppi, du', '23', 'lala']
// Empty CSV string
let result = CSVtoArray("");
console.log(result); // []
// CSV string with two empty values
let result = CSVtoArray(",");
console.log(result); // ['', '']
// Double quoted CSV string having single quoted values
let result = CSVtoArray("'one','two with escaped \' single quote', 'three, with, commas'");
console.log(result); // ['one', 'two with escaped \' single quote', 'three, with, commas']
// Single quoted CSV string having double quoted values
let result = CSVtoArray('"one","two with escaped \" double quote", "three, with, commas"');
console.log(result); // ['one', 'two with escaped " double quote', 'three, with, commas']
// CSV string with whitespace in and around empty and non-empty values
let result = CSVtoArray(" one , 'two' , , ' four' ,, 'six ', ' seven ' , ");
console.log(result); // ['one', 'two', '', 'four', '', 'six ', ' seven ']
// Not valid
let result = CSVtoArray("one, that's me!, escaped \, comma");
console.log(result); // nullThis solution ensures accurate parsing of CSV strings, handling quoted fields containing commas while adhering to the specified requirements.
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