javascript - 如何在 chart.js 中将日期显示为 x 轴上的标签

标签 javascript php html chart.js

我正在尝试使用 chart.js 在 x.axix 上显示日期。我从数据库中收到两个 json 值；时间戳和传感器读取。我想根据图表中的每个时间戳显示传感器读数的刻度。数据每隔几分钟定期更新一次。

这是时间戳的格式:

2018-12-07 12:45:17

到目前为止，这是我的图表代码:

var ctx = document.getElementById ('myChart').getContext('2d');
    var myChart = new Chart(ctx, {
    type: 'line',
    data: {
    labels: time_Array, // example value 2018-12-07 12:45:17 .......
    datasets: [{
    label: 'Humidity',
    data: meas_value_Array, //// example value 116, 120 110 ....
    backgroundColor: "rgba(255,153,0,0.4)"
    }]
    },

        options: {
        scales: {
            yAxes: [{
                ticks: {
                    beginAtZero:true
                }
            }],
            xAxes: [{
                type: 'time',
                time: {
                    unit: 'minute',
                    displayFormats: {
                        second: 'h:MM:SS',
                        minute: 'h:MM',
                        hour: 'hA',
                        day: 'MMM D',
                        month: 'YYYY MMM',
                        year: 'YYYY'
                    },                            
                },
                display: true,
                scaleLabel: {
                    display: true,
                    labelString: 'value'
                }                        
            }]                    
        }
    }
});

它在 firefox 中引发此错误:

TypeError: i.min is undefined[Learn More] Chart.min.js:14:18390
determineDataLimits
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:14:18390
update
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:13:2110
n
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:12:23263
[26]</e.exports/o.each
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:12:8324
update
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:12:24692
updateLayout
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:11:30363
update
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:11:30126
[23]</e.exports/t.Controller
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:11:27625
t
https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js:12:22144
dspChrt3

虽然 chrome 显示此错误:

Uncaught TypeError: Cannot read property 'call' of undefined
    at a.determineDataLimits (Chart.min.js:14)
    at a.update (Chart.min.js:13)
    at n (Chart.min.js:12)
    at Object.o.each (Chart.min.js:12)
    at Object.update (Chart.min.js:12)
    at t.Controller.updateLayout (Chart.min.js:11)
    at t.Controller.update (Chart.min.js:11)
    at new t.Controller (Chart.min.js:11)
    at new t (Chart.min.js:12)
    at dspChrt3 (chart3.php:30)

这是我尝试添加数组值硬编码的代码片段:

   
        var time_Array = ["2018-12-07 15:45:17", "2018-12-07 15:30:17", "2018-12-07 15:15:16", "2018-12-07 15:00:17", "2018-12-07 14:45:16", "2018-12-07 14:30:17", "2018-12-07 14:15:17", "2018-12-07 14:00:17", "2018-12-07 13:45:17", "2018-12-07 13:30:16", "2018-12-07 13:15:17", "2018-12-07 16:00:17"];
        var meas_value_Array = [121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121];


        //console.log(time_Array);
        //console.log(meas_value_Array);

        var ctx = document.getElementById ('myChart').getContext('2d');
        var myChart = new Chart(ctx, {
        type: 'line',
        data: {
        labels: time_Array,
        datasets: [{
        label: 'Humidity',
        data: meas_value_Array,
        backgroundColor: "rgba(255,153,0,0.4)"
        }]
        },

            options: {
            scales: {
                yAxes: [{
                    ticks: {
                        beginAtZero:true
                    }
                }],
                xAxes: [{
                    type: 'time',
                    time: {
                        unit: 'minute',
                        displayFormats: {
                            second: 'h:MM:SS',
                            minute: 'h:MM',
                            hour: 'hA',
                            day: 'MMM D',
                            month: 'YYYY MMM',
                            year: 'YYYY'
                        },                            
                    },
                    display: true,
                    scaleLabel: {
                        display: true,
                        labelString: 'value'
                    }                        
                }]                    
            }
        }
    });
   
<script src="https://rawgit.com/moment/moment/2.2.1/min/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js"></script>


<html>
<meta charset="utf-8">
<script src="https://rawgit.com/moment/moment/2.2.1/min/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js"></script>

<body>
<canvas id="myChart"></canvas>

</body>
</html>

这是我的整个 JS 代码:

   var Device_Data;
   var temperature, meas_value;


   function dspChrt3(Device_Data) { 
        //console.log(Device_Data);

        var time_Array = [];
        var meas_value_Array = [];

       for(var i=0; i<Device_Data.length; i++) {
            time_Array.push(Device_Data[i].date_time);
            meas_value_Array.push(Device_Data[i].meas_value);
            }

        console.log(Device_Data[0].date_time);
        console.log(Device_Data[1].meas_value);
        date_time = Device_Data[0].date_time;
        meas_value = Device_Data[1].meas_value;
        time_Array.shift();
        time_Array.push(date_time);
        meas_value_Array.shift();
        meas_value_Array.push(meas_value);

        //console.log(time_Array);
        //console.log(meas_value_Array);

        var ctx = document.getElementById ('myChart11').getContext('2d');
        var myChart = new Chart(ctx, {
        type: 'line',
        data: {
        labels: time_Array,
        datasets: [{
        label: 'Humidity',
        data: meas_value_Array,
        backgroundColor: "rgba(255,153,0,0.4)"
        }]
        },

            options: {
            scales: {
                yAxes: [{
                    ticks: {
                        beginAtZero:true
                    }
                }],
                xAxes: [{
                    type: 'time',
                    time: {
                        unit: 'minute',
                        displayFormats: {
                            second: 'h:MM:SS',
                            minute: 'h:MM',
                            hour: 'hA',
                            day: 'MMM D',
                            month: 'YYYY MMM',
                            year: 'YYYY'
                        },                            
                    },
                    display: true,
                    scaleLabel: {
                        display: true,
                        labelString: 'value'
                    }                        
                }]                    
            }
        }
    });
    }

最佳答案

如果我没理解错，那么您只希望 x 轴为日期，即 2018-12-07 15:45:17。我已经设法做到了。这是我的全部代码。之前没有使用过 chart.js，也没有太多时间来正确查看，而是查看 displayFormats 并更改您想要的方式。希望这会有所帮助。

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.3/Chart.bundle.js"></script>

<body>
<canvas id="myChart" width="400" height="400"></canvas>

<script>
$(document).ready(function(){
        var time_Array = ["2018-12-07 15:45:17", "2018-12-07 15:30:17", "2018-12-07 15:15:16", "2018-12-07 15:00:17", "2018-12-07 14:45:16", "2018-12-07 14:30:17", "2018-12-07 14:15:17", "2018-12-07 14:00:17", "2018-12-07 13:45:17", "2018-12-07 13:30:16", "2018-12-07 13:15:17", "2018-12-07 16:00:17"];
        var meas_value_Array = [121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121];


        //console.log(time_Array);
        //console.log(meas_value_Array);

        var ctx = document.getElementById ('myChart').getContext('2d');
        var myChart = new Chart(ctx, {
        type: 'line',
        data: {
        labels: time_Array,
        datasets: [{
        label: 'Humidity',
        data: meas_value_Array,
        backgroundColor: "rgba(255,153,0,0.4)"
        }]
        },

            options: {
            scales: {
                yAxes: [{
                    ticks: {
                        beginAtZero:true
                    }
                }],
                xAxes: [{
                    type: 'time',
                    time: {
                        parser: 'YYYY-MM-DD HH:mm:ss',
                        unit: 'minute',
                        displayFormats: {
                            'minute': 'YYYY-MM-DD HH:mm:ss',
                            'hour': 'YYYY-MM-DD HH:mm:ss'
                        }
                    },
                    ticks: {
                        source: 'data'
                    }
                }]                    
            }
        }
    });
});
</script>

</body>
</html>

关于javascript - 如何在 chart.js 中将日期显示为 x 轴上的标签，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53669361/

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