What could be the reason for TypeScript showing the error "Type 'unknown' has no property 'value'"?

Here is a function that I have:

myChart.on('click', { targetType: 'axisLabel' }, params => {
      var uri = window.location.hash.replace("#", "");
      this.router.navigate([uri + '/trips', params.value]);
    })

However, when using this function, an error message is returned:

Property 'value' does not exist on type 'unknown'.

The params object actually contains the property value. How can I fix this recurring error?

Answer №1

Ensuring a type annotation for params is crucial. Without it, the compiler lacks the necessary information to determine whether the value property exists.

For example:

interface Parameters {
    value: string
}

myChart.on('click', { targetType: 'axisLabel' }, (params: Parameters): void => {
    var uri = window.location.hash.replace("#", "");
    this.router.navigate([uri + '/trips', params.value]);
});

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