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String API: string.startsWith()

Determines whether a string begins with the characters of another string.

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str.startsWith(searchString) determines whether str begins with searchString.

the 1st parameter, the string to search for

  • can be just a character
  • can be a string
  • can contain unicode characters
  • a regular expression throws a TypeError

the 2nd parameter, the position where to start searching from

  • e.g. find "str" at position 4
  • for undefined is the same as 0
  • the parameter gets converted to an int
  • a value larger than the string`s length, returns false

this functionality can be used on non-strings too

  • e.g. a boolean
  • e.g. a number
  • also using the position works


The official specification, actually quite good to read for this function.
The Mozilla Developer Network docs, contains good examples.