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String API: string.trimStart()

string.trimStart() - removes whitespace from the beginning of a string

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string.trimStart() removes whitespace from the beginning of a string

  • trimStart() method is defined on every string (on the prototype)

GIVEN a string starting with one space

  • WHEN the string is only a space THEN trimStart leave an empty string
  • WHEN followed by a word THEN just the word will be left
  • WHEN followed by a word and then spaces THEN the word and the spaces after will be left
  • WHEN trimming a right-to-left (RTL) string THEN spaces are still trimmed from the left side
  • WHEN trimming a russian (cyrillic) string THEN gets trimmed on the left too
  • WHEN followed by a UTF string THEN it also removes the leading space

GIVEN a string starting with any number of spaces

  • WHEN starting without a space THEN trimStart() will leave the string as is
  • WHEN starting with many spaces THEN those will be trimmed only at the start (left for a left-to-right language)
  • WHEN trimming a RTL string THEN it spaces are removed from the left, ignoring the string direction
  • WHEN a string starts with spaces and line breaks THEN those are removed too

additional knowledge

  • WHEN trimStart() is called THEN the original string stays untouched
  • trimLeft and trimStart are the same function

Links

Description of `String.prototype.trimStart()` on MDN.
The specification describing `String.prototype.trimStart()`.
The official tests for JavaScript (engines) for `trimStart`.