Struggling to get my chart to render dynamically in vue-chartjs

Question

Struggling to get my chart to render dynamically in vue-chartjs

In my MainChart.vue file, I defined my chart like this:

import { Line, mixins } from 'vue-chartjs'
const { reactiveProp } = mixins
// const brandPrimary = '#20a8d8'
export default {
  extends: Line,
  mixins: [reactiveProp],
  props: ['options', 'chartData', 'height'],
  mounted () {
    this.renderChart(this.chartData, this.options)
    var elements = 1
  }
}

I ran a test on this code and it worked perfectly.

<line-chart :chartData="myChartData"></line-chart>

However, when I attempted to render the chart dynamically, it didn't work.

import lineChart from './MainChart';

// ...

let chartClass = Vue.extend(lineChart)
let chartInstance = new chartClass({
  propsData: {
    chartData: myChartData
  }
})
chartInstance.$mount()
console.log(chartInstance.$el)
console.log(chartInstance.$el.querySelector("canvas").toDataURL('image/png'))
console.log(chartInstance.$refs.canvas)
console.log(chartInstance.$refs.canvas.toDataURL('image/png'))

When checking the console messages, I noticed that nothing was being drawn in the canvas area.

How can I go about rendering my chart dynamically?

For more information, please refer to these related questions:

Is it possible to print a chart with vue-chartjs?

javascript vue.js vue-chartjs

Answer 1

Answer №1

If you are looking to retrieve complete image data, it is essential to wait until the chart rendering process is completed. Utilizing a 'Promise' can be quite beneficial in this scenario.

 async function generateChart(data, index, width, height) {
  var canvas = document.createElement("canvas");
  canvas.width = 765;
  canvas.height = 382;
  //canvas.style.width = "765px";
  //canvas.style.height = "382px";
  //canvas.style.display = "none";
  canvas.id = "dynamicChart";
  document.body.appendChild(canvas);

  var ctx = document.getElementById("dynamicChart").getContext('2d');
  var draw = () => new Promise((resolve, reject) => {
   new Chart(ctx, {
    type: 'bar',
    data: data,
    options: {
     responsive: false
    }
   })
   setTimeout(() => resolve(), 100);
  });

  await draw();

  let imageData = document.getElementById("dynamicChart").toDataURL("image/png");
  console.log(imageData);

  addImage(imageData, index, width, height);
  document.body.removeChild(canvas);
 }

 // ...

 await generateChart(myChartData, 0, 400, 300);

If you need to plot multiple charts within a loop, consider using this approach:

let chartFunctions = [];
myList.forEach((item) => {
  chartFunctions.push(async function() {
    await generateChart(myChartData, 3, 160, 80);
  });
}

for(let k in chartFunctions) {
  await chartFunctions[k]();
}

Check out these console messages for more details:

https://i.sstatic.net/l93xc.png

Answer 2

If you are looking to retrieve complete image data, it is essential to wait until the chart rendering process is completed. Utilizing a 'Promise' can be quite beneficial in this scenario.

 async function generateChart(data, index, width, height) {
  var canvas = document.createElement("canvas");
  canvas.width = 765;
  canvas.height = 382;
  //canvas.style.width = "765px";
  //canvas.style.height = "382px";
  //canvas.style.display = "none";
  canvas.id = "dynamicChart";
  document.body.appendChild(canvas);

  var ctx = document.getElementById("dynamicChart").getContext('2d');
  var draw = () => new Promise((resolve, reject) => {
   new Chart(ctx, {
    type: 'bar',
    data: data,
    options: {
     responsive: false
    }
   })
   setTimeout(() => resolve(), 100);
  });

  await draw();

  let imageData = document.getElementById("dynamicChart").toDataURL("image/png");
  console.log(imageData);

  addImage(imageData, index, width, height);
  document.body.removeChild(canvas);
 }

 // ...

 await generateChart(myChartData, 0, 400, 300);

If you need to plot multiple charts within a loop, consider using this approach:

let chartFunctions = [];
myList.forEach((item) => {
  chartFunctions.push(async function() {
    await generateChart(myChartData, 3, 160, 80);
  });
}

for(let k in chartFunctions) {
  await chartFunctions[k]();
}

Check out these console messages for more details:

https://i.sstatic.net/l93xc.png

Struggling to get my chart to render dynamically in vue-chartjs

Answer №1

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