Write JSON-formatted output to a java.io.Writer. Options are key-value pairs, valid options are: :escape-unicode boolean If true (default) non-ASCII characters are escaped as \uXXXX :escape-js-separators boolean If true (default) the Unicode characters U+2028 and U+2029 will be escaped as \u2028 and \u2029 even if :escape-unicode is false. (These two characters are valid in pure JSON but are not valid in JavaScript strings.) :escape-slash boolean If true (default) the slash / is escaped as \/ :key-fn function Single-argument function called on map keys; return value will replace the property names in the output. Must return a string. Default calls clojure.core/name on symbols and keywords and clojure.core/str on everything else. :value-fn function Function to transform values in maps before writing. For each key-value pair in an input map, called with two arguments: the key (BEFORE transformation by key-fn) and the value. The return value of value-fn will replace the value in the output. If the return value is a number, boolean, string, or nil it will be included literally in the output. If the return value is a non-map collection, it will be processed recursively. If the return value is a map, it will be processed recursively, calling value-fn again on its key-value pairs. If value-fn returns itself, the key-value pair will be omitted from the output. This option does not apply to non-map collections.