How to clear a chart from a canvas so that hover events cannot be triggered?

I had huge problems with this

First I tried .clear() then I tried .destroy() and I tried setting my chart reference to null

What finally fixed the issue for me: deleting the <canvas> element and then reappending a new <canvas> to the parent container

My specific code (obviously there's a million ways to do this):

var resetCanvas = function(){
  $('#results-graph').remove(); // this is my <canvas> element
  $('#graph-container').append('<canvas id="results-graph"><canvas>');
  canvas = document.querySelector('#results-graph');
  ctx = canvas.getContext('2d');
  ctx.canvas.width = $('#graph').width(); // resize to parent width
  ctx.canvas.height = $('#graph').height(); // resize to parent height
  var x = canvas.width/2;
  var y = canvas.height/2;
  ctx.font = '10pt Verdana';
  ctx.textAlign = 'center';
  ctx.fillText('This text is centered on the canvas', x, y);
};

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I have faced the same problem few hours ago.

The ".clear()" method actually clears the canvas, but (evidently) it leaves the object alive and reactive.

Reading carefully the official documentation, in the "Advanced usage" section, I have noticed the method ".destroy()", described as follows:

"Use this to destroy any chart instances that are created. This will clean up any references stored to the chart object within Chart.js, along with any associated event listeners attached by Chart.js."

It actually does what it claims and it has worked fine for me, I suggest you to give it a try.

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var myPieChart=null;

function drawChart(objChart,data){
    if(myPieChart!=null){
        myPieChart.destroy();
    }
    // Get the context of the canvas element we want to select
    var ctx = objChart.getContext("2d");
    myPieChart = new Chart(ctx).Pie(data, {animateScale: true});
}

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This is the only thing that worked for me:

document.getElementById("chartContainer").innerHTML = ' ';
document.getElementById("chartContainer").innerHTML = '<canvas id="myCanvas"></canvas>';
var ctx = document.getElementById("myCanvas").getContext("2d");

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I had the same problem here... I tried to use destroy() and clear() method, but without success.

I resolved it the next way:

HTML:

<div id="pieChartContent">
    <canvas id="pieChart" width="300" height="300"></canvas>
</div>

Javascript:

var pieChartContent = document.getElementById('pieChartContent');
pieChartContent.innerHTML = ' ';
$('#pieChartContent').append('<canvas id="pieChart" width="300" height="300"><canvas>');

ctx = $("#pieChart").get(0).getContext("2d");        
var myPieChart = new Chart(ctx).Pie(data, options);

It works perfect to me... I hope that It helps.

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We can update the chart data in Chart.js V2.0 as follows:

var myChart = new Chart(ctx, data);
myChart.config.data = new_data;
myChart.update();

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This worked very well for me

    var ctx = $("#mycanvas");
     var LineGraph = new Chart(ctx, {
        type: 'line',
        data: chartdata});
        LineGraph.destroy();

Use .destroy this to destroy any chart instances that are created. This will clean up any references stored to the chart object within Chart.js, along with any associated event listeners attached by Chart.js. This must be called before the canvas is reused for a new chart.

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Simple edit for 2020:

This worked for me. Change the chart to global by making it window owned (Change the declaration from var myChart to window myChart)

Check whether the chart variable is already initialized as Chart, if so, destroy it and create a new one, even you can create another one on the same name. Below is the code:

if(window.myChart instanceof Chart)
{
    window.myChart.destroy();
}
var ctx = document.getElementById('myChart').getContext("2d");

Hope it works!

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It's best to use Chart.js specific functionalities to initially check for the existing chart instance and then perform destroy or clear in order to reuse the same canvas element for rendering another chart, instead of handlding HTML elements from within JS.

ChartJs's getChart(key) - finds the chart instance from the given key.

If the key is a string, it is interpreted as the ID of the Canvas element for the Chart.

The key can also be a CanvasRenderingContext2D or an HTMLDOMElement.

Note: This will return undefined if no Chart is found. If the instance of the chart is found, it signifies that the chart must have previously been created.

// JS - Destroy exiting Chart Instance to reuse element let chartStatus = Chart.getChart("myChart"); // id if (chartStatus != undefined) { chartStatus.destroy(); //(or) // chartStatus.clear(); } //-- End of chart destroy var chartCanvas = $('#myChart'); // id chartInstance = new Chart(chartCanvas, { type: 'line', data: data });

This approach would save you from remove - create - append a Canvas element into DIV from inside JS.

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Complementing Adam's Answer

With Vanilla JS:

document.getElementById("results-graph").remove(); //canvas div = document.querySelector("#graph-container"); //canvas parent element div.insertAdjacentHTML("afterbegin", ""); //adding the canvas again

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Using CanvasJS, this works for me clearing chart and everything else, might work for you as well, granting you set your canvas/chart up fully before each processing elsewhere:

var myDiv= document.getElementById("my_chart_container{0}";
myDiv.innerHTML = "";

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I couldn't get .destroy() to work either so this is what I'm doing. The chart_parent div is where I want the canvas to show up. I need the canvas to resize each time, so this answer is an extension of the above one.

HTML:

<div class="main_section" > <div id="chart_parent"></div> <div id="legend"></div> </div>

JQuery:

  $('#chart').remove(); // this is my <canvas> element
  $('#chart_parent').append('<label for = "chart">Total<br /><canvas class="chart" id="chart" width='+$('#chart_parent').width()+'><canvas></label>');

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When you create one new chart.js canvas, this generate one new iframe hidden, you need delete the canvas and the olds iframes.

$('#canvasChart').remove(); 
$('iframe.chartjs-hidden-iframe').remove(); 
$('#graph-container').append('<canvas id="canvasChart"><canvas>'); 
var ctx = document.getElementById("canvasChart"); 
var myChart = new Chart(ctx, { blablabla });

reference: https://github.com/zebus3d/javascript/blob/master/chartJS_filtering_with_checkboxs.html

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This worked for me. Add a call to clearChart, at the top oF your updateChart()

`function clearChart() {
    event.preventDefault();
    var parent = document.getElementById('parent-canvas');
    var child = document.getElementById('myChart');          
    parent.removeChild(child);            
    parent.innerHTML ='<canvas id="myChart" width="350" height="99" ></canvas>';             
    return;
}`

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Since destroy kind of destroys "everything", a cheap and simple solution when all you really want is to just "reset the data". Resetting your datasets to an empty array will work perfectly fine as well. So, if you have a dataset with labels, and an axis on each side:

window.myLine2.data.labels = [];
window.myLine2.data.datasets[0].data = [];
window.myLine2.data.datasets[1].data = [];

After this, you can simply call:

window.myLine2.data.labels.push(x);
window.myLine2.data.datasets[0].data.push(y);

or, depending whether you're using a 2d dataset:

window.myLine2.data.datasets[0].data.push({ x: x, y: y});

It'll be a lot more lightweight than completely destroying your whole chart/dataset, and rebuilding everything.

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If you are using chart.js in an Angular project with Typescript, the you can try the following;

Import the library:
    import { Chart } from 'chart.js';

In your Component Class declare the variable and define a method:

  chart: Chart;

  drawGraph(): void {
    if (this.chart) {
      this.chart.destroy();
    }

    this.chart = new Chart('myChart', {
       .........
    });
  }


In HTML Template:
<canvas id="myChart"></canvas>

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What we did is, before initialization of new chart, remove/destroy the previews Chart instance, if exist already, then create a new chart, for example

if(myGraf != undefined)
    myGraf.destroy();
    myGraf= new Chart(document.getElementById("CanvasID"),
    { 
      ...
    }

Hope this helps.

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First put chart in some variable then history it next time before init

#Check if myChart object exist then distort it

    if($scope.myChart) {
      $scope.myChart.destroy();
    }

    $scope.myChart  = new Chart(targetCanvas

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You should save the chart as a variable. On global scope, if its pure javascript, or as a class property, if its Angular.

Then you'll be able to use this reference to call destroy().

Pure Javascript:

var chart;

function startChart() {
    // Code for chart initialization
    chart = new Chart(...); // Replace ... with your chart parameters
}

function destroyChart() {
    chart.destroy();
}

Angular:

export class MyComponent {
    chart;

    constructor() {
        // Your constructor code goes here
    }

    ngOnInit() {
        // Probably you'll start your chart here

        // Code for chart initialization
        this.chart = new Chart(...); // Replace ... with your chart parameters
    }

    destroyChart() {
        this.chart.destroy();
    }
}

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For me this worked:

var in_canvas = document.getElementById('chart_holder'); //remove canvas if present while (in_canvas.hasChildNodes()) { in_canvas.removeChild(in_canvas.lastChild); } //insert canvas var newDiv = document.createElement('canvas'); in_canvas.appendChild(newDiv); newDiv.id = "myChart";

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Chart.js has a bug: Chart.controller(instance) registers any new chart in a global property Chart.instances[] and deletes it from this property on .destroy().

But at chart creation Chart.js also writes ._meta property to dataset variable:

var meta = dataset._meta[me.id];
if (!meta) {
   meta = dataset._meta[me.id] = {
       type: null,
       data: [],
       dataset: null,
       controller: null,
       hidden: null,     // See isDatasetVisible() comment
       xAxisID: null,
       yAxisID: null
   };

and it doesn't delete this property on destroy().

If you use your old dataset object without removing ._meta property, Chart.js will add new dataset to ._meta without deletion previous data. Thus, at each chart's re-initialization your dataset object accumulates all previous data.

In order to avoid this, destroy dataset object after calling Chart.destroy().

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for those who like me use a function to create several graphics and want to update them a block too, only the function .destroy() worked for me, I would have liked to make an .update(), which seems cleaner but ... here is a code snippet that may help.

var SNS_Chart = {};

// IF LABELS IS EMPTY (after update my datas)
if( labels.length != 0 ){

      if( Object.entries(SNS_Chart).length != 0 ){

            array_items_datas.forEach(function(for_item, k_arr){
                SNS_Chart[''+for_item+''].destroy();
            });

       }

       // LOOP OVER ARRAY_ITEMS
       array_items_datas.forEach(function(for_item, k_arr){

             // chart
             OPTIONS.title.text = array_str[k_arr];
             var elem = document.getElementById(for_item);
             SNS_Chart[''+for_item+''] = new Chart(elem, {
                 type: 'doughnut',
                 data: {
                     labels: labels[''+for_item+''],
                     datasets: [{
                        // label: '',
                        backgroundColor: [
                            '#5b9aa0',
                            '#c6bcb6',
                            '#eeac99',
                            '#a79e84',
                            '#dbceb0',
                            '#8ca3a3',
                            '#82b74b',
                            '#454140',
                            '#c1502e',
                            '#bd5734'
                        ],
                        borderColor: '#757575',
                        borderWidth : 2,
                        // hoverBackgroundColor : '#616161',
                        data: datas[''+for_item+''],
                     }]
                 },
                 options: OPTIONS

             });
             // chart
       });
       // END LOOP ARRAY_ITEMS

  }
 // END IF LABELS IS EMPTY ...

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just declare let doughnut = null before creating your chart

const doughnutDriverStatsChartCanvas = $('#dougnautChartDriverStats').get(0).getContext('2d')
const doughnutOptionsDriverStats = {
    maintainAspectRatio: false,
    responsive: true,
}
let doughnut = null
doughnut = new Chart(doughnutDriverStatsChartCanvas, {
    type: 'doughnut',
    data: doughnutChartDriverStats,
    options: doughnutOptionsDriverStats
})

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