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5. Query string

Available inall subroutines.

Returns a value associated with the name in the query component of an URL.

If the query component does not contain a value associated with name, then querystring.get returns a not set value. For example, querystring.get("/?a=1&b=2&c=3", "d") is a not set value.

If a query parameter associated with name is found but the value is absent, then querystring.get returns the string "". For example, querystring.get("/?a=1&b=&c=3", "b") is "".

If multiple query parameters of the same name are present in the query component, then querystring.get returns the first value associated with name. For example, querystring.get("/?a=1&b=2&c=3&b=4&d=5", "b") is "2".

If the URL does not include a query component, then querystring.get returns a not set value. For example, querystring.get("/", "a") is a not set value.

If querystring.get is called with not set or empty string arguments, then it returns a not set value. For example, querystring.get("", "") is a not set value.

To check if the return value is not an empty string or a not set value, use the std.strlen function, which returns 0 in both cases.

if (std.strlen(querystring.get(req.url, "foo")) > 0) {
    // Do something if the value associated with "foo" is not an empty string
    // or a not set value.
}

This function conforms to the URL Living Standard.

Examples

querystring.get("/?foo=", "foo") # returns ""
querystring.get("", "") # returns a not set value
querystring.get("/?foo=&foo=bar", "foo") # returns ""
querystring.get("/?a=1&b=2&c=3&d=4", "b") # returns "2"
querystring.get("/?a=1", "b") # returns a not set value
querystring.get("/?foo", "foo") # returns a not set value
querystring.get("/?a=1&b=2&c=3&d=4&b=5", "b") # returns "2"
querystring.get(not set string, not set string) # returns a not set value