QGIS/resources/function_help/json/replace

{
  "function": "replace",
  "description": "Returns a string with the the supplied string replaced.",
  "arguments": [ {"arg":"string","description":"the input string"},
                 {"arg":"before","description":"the string to replace"},
                 {"arg":"after","description":"the string to use as a replacement"}],
  "examples": [ { "expression":"replace('QGIS SHOULD ROCK','SHOULD','DOES')", "returns":"'QGIS DOES ROCK'"}
  ]
}