こちらにあるデータをサンプルとして使います。
新型コロナワクチンの接種状況（高齢者等）
「都道府県別接種回数詳細」 です。
prefecture.ndjson をダウンロードします。
これを、栃木県の 2021-06-05 だけのものにします。
awk '/"prefecture":"09"/{print $0}' prefecture.ndjson > tochigi.ndjson
awk '/"date":"2021-06-05"/{print $0}' tochigi.ndjson > tochigi_jun05.ndjson
tochigi_jun05.ndjson
{"date":"2021-06-05","prefecture":"09","gender":"F","age":"-64","medical_worker":false,"status":1,"count":28}
{"date":"2021-06-05","prefecture":"09","gender":"F","age":"-64","medical_worker":false,"status":2,"count":2}
{"date":"2021-06-05","prefecture":"09","gender":"F","age":"65-","medical_worker":false,"status":1,"count":1380}
{"date":"2021-06-05","prefecture":"09","gender":"F","age":"65-","medical_worker":false,"status":2,"count":245}
{"date":"2021-06-05","prefecture":"09","gender":"M","age":"-64","medical_worker":false,"status":1,"count":28}
{"date":"2021-06-05","prefecture":"09","gender":"M","age":"-64","medical_worker":false,"status":2,"count":4}
{"date":"2021-06-05","prefecture":"09","gender":"M","age":"65-","medical_worker":false,"status":1,"count":1031}
{"date":"2021-06-05","prefecture":"09","gender":"M","age":"65-","medical_worker":false,"status":2,"count":192}
{"date":"2021-06-05","prefecture":"09","gender":"U","age":"UNK","medical_worker":false,"status":1,"count":1}
必要なライブラリーのインストール
sudo npm install -g ndjson
ex01.js
#! /usr/bin/node
// ---------------------------------------------------------------
// ex01.js
//
// Jun/06/2021
// ---------------------------------------------------------------
'use strict'
const ndjson = require('ndjson')
var fs = require("fs")
const file_in = 'tochigi_jun05.ndjson'
fs.createReadStream(file_in)
.pipe(ndjson.parse())
.on('data', function(obj) {
// obj is a javascript object
console.log(obj)
})
// ---------------------------------------------------------------
実行
export NODE_PATH=/usr/lib/node_modules
./ex01.js
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