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String.prototype.split(separator) accepts not only a fixed string but also a regex as separator. This makes it a powerful tool to tokenize structured text.

'uno, due,tre  quattro'.split(/[,\s]+/);
// ["uno", "due", "tre", "quattro"]

The regex /[,\s]+/ matches "one or more of comma or whitespace": split splits on any compound delimiter.

Typical cases

• Permissive CSV: text.split(/\s*,\s*/) to handle spaces around commas.
• Naive tokenizer: text.split(/\s+/) to extract words.
• Keep the separator: if the regex contains capturing groups, the content of the groups is included in the result array.

'a=1; b=2; c=3'.split(/(;)\s*/);
// ["a=1", ";", "b=2", ";", "c=3"]

Without the () group the semicolon would disappear. With (;) you keep it in the result.

Preserving separators in split operations

If you place split separators inside capturing parentheses, the output of String.prototype.split will include the separators themselves as elements in the final array, instead of discarding them.

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