streaming command line newline-delimited json reducing utility modeled after jsonmap
$ npm install jsonreduce -gthis will be each line of JSON that gets parsed out of the incoming newline-delimited json stream. Two arguments will be provided, previous and current. current is the current line being parsed while previous is the memoized value (same as this).
$ echo '{"foo": "bar"}\n{"baz": "taco"}' | jsonreduce 'this.keys = this.keys.concat(Object.keys(current))' --memo '{"keys": []}'
{"keys":["foo","baz"]}MIT