The dataLabels formatter requires type definitions because it allows (string | number)[].

[daiboom]

Description

I try setting the return value of the data label formatter to [val, 1, 'string']. Although a warning appears saying that this is not a valid return type for the formatter, ApexCharts.js actually accepts it and displays it on the chart.

Steps to Reproduce

var options = {
  chart: {
    type: "bar"
  },
  series: [
    {
      name: "sales",
      data: [30, 40, 45, 50, 49, 60, 70, 91, 125]
    }
  ],
  xaxis: {
    categories: [1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999]
  },
  dataLabels: {
    formatter: (val, opt) => {
      return [val, 1, "string"];
    }
  }
};

var chart = new ApexCharts(document.querySelector("#chart"), options);

chart.render();

// apexcharts.d.ts

type ApexDataLabels = {
...
  [-] formatter?(val: string | number | number[], opts?: any): string | number | string[]
  [+] formatter?(val: string | number | number[], opts?: any): string | number | (string | number)[]
}

Reproduction Link

https://codepen.io/choidaeboem/pen/OJKraap