我有一个用固定数据提供图表的函数：

function drawChart() {
    var data = google.visualization.arrayToDataTable([
        ['Date','CPU Temp'],['2004',340],['2005',460],['2006',1120],['2007',540]
    ]);
}

我想用从包含两列：date 和 temperature 的数据库表中读取的数据替换固定数据。读取的数据存储在 $json 变量中：

[
  {"datain":"2021-04-20 12:00:03","temp":"39.2"},{"datain":"2021-04-21 00:00:05","temp":"40.2"},{"datain":"2021-04-21 12:00:03","temp":"40.8"},{"datain":"2021-08-01 12:00:12","temp":"47.2"}
]

这是我的错误代码：

let date= "";
let temp = "";
for (let i = 0; i < <?php echo count($json)?>; i++){
    date = <?php echo $json[0] ?>;
    temp = <?php echo $json[1] ?>;
}
  
function drawChart() {
    var data = google.visualization.arrayToDataTable([
        ['Date',[date,temp]
    ]);
}

我怎样才能做到这一点？

编辑： 使用@trincot 的建议编辑后的代码：

< script type = "text/javascript" >
  google.charts.load('current',{
    'packages': ['corechart']
  });
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Date','Temp'],...<?php echo $json; ?>.map(({
      datain,temp
    }) => [new Date(datain),parseFloat(temp)])
  ]);

  var options = {
    title: 'CPU Temp History',curveType: 'function',legend: {
      position: 'bottom'
    }
  };

  var chart = new google.visualization.LineChart(document.getElementById('curve_chart'));

  chart.draw(data,options);
} <
/script>

原始代码在这里：chart code