Access data about chart js instance and component variable

Question

I have the following onClick function inside my ChartJS instance. It works perfectly to access component variables.

onClick: () => {
    console.log(this.test);
  },

Now I need to get some informations about the chart.

For example:

Using this function bellow I can access event of click and array but I can't access component variable like in the first arrow function

chartClickEvent(event, array) {
    const ENTRADA = 0, SAIDA = 1;
    if (array[0]) {
      let columnIndex = array[0]._index;
      if (columnIndex == ENTRADA) {
        console.log(this.test);
      }
    }
  }

It's shows undefined when I try to print component variable

onClick: chartClickEvent,

How to access both? Data about chart and component variable

onClick: (event, array) => this.chartClickEvent(event, array) — David
– David, Commented Jun 28, 2019 at 12:38
@David it's works like a charm. Could you create a answer for that? — renanvm
– renanvm, Commented Jun 28, 2019 at 12:42

youri · Accepted Answer · 2019-06-28 12:40:02Z

1

Use the Function.prototype.bind function:

onClick: chartClickEvent.bind(this)

What happens here is when chartClickEvent is being executed the scope is different and so the this is not what you expected.

The bind function returns a new function that is bound to the this you defined.

You can, of course, use an arrow function there as well:

onClick: (event, array) => chartClickEvent(event, array)

answered Jun 28, 2019 at 12:40

youri

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1 Comment

renanvm Over a year ago

Thank you man. David answered first in the comments area but If he does not create a answer I going to accept yours

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