Function getSingleQueryParam

Returns the first value for the specified key in the query object. If pred specified, returns the first value that meets it.

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返り値は、指定した key に対応するパラメータのうち最初の値。 もし pred が指定されている場合は、その関数に合格した値のうち最初のものが返る。

Example

getSingleQueryParam({},            "id") === undefined
getSingleQueryParam({ id: "aaa" }, "id") === "aaa"

// with pred specified
const is_a = (s: string) => s === "a"
getSingleQueryParam({ id: "a" },        "id", is_a) === "a"
getSingleQueryParam({},                 "id", is_a) === undefined
getSingleQueryParam({ id: "b" },        "id", is_a) === undefined
getSingleQueryParam({ id: ["b", "a"] }, "id", is_a) === "a"
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Param: pred

optional. the first value that fits this predicate will be returned.