Sometimes, we want to fix the “Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index” error with TypeScript.

In this article, we’ll look at how to fix the “Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index” error with TypeScript.

How to fix the “Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index” error with TypeScript?

To fix the “Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index” error with TypeScript, we should set the type of the array elements.

For instance, we write

interface TrainInfo {
  name: keyof typeof plotOptions;
  x: Array<number>;
  y: Array<number>;
  type: string;
  mode: string;
}

const allPlotData: Array<TrainInfo> = [
  {
    name: "train1",
    x: [],
    y: [],
    type: "scatter",
    mode: "lines",
  },
  // ...
];
const plotData = allPlotData.filter(({ name }) => plotOptions[name]);

to set the type of the allPlotData array to Array<TrainInfo>

TrainInfo is the type of each entry.

Then we can call allPlotData.filter without any TypeScript compiler errors.

Conclusion

To fix the “Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index” error with TypeScript, we should set the type of the array elements.