How can I make an empty string array in Typescript?

Outside of a method:

arr: string[] = [];

The definition of string array should be:

// instead of this
// var errors: [string];
// we need this
var errors: string[];
errors = [];

Note: another issue could be the parameter key here

...forEach(function (key) {...

I would guess that we often should declare two of them, because first is very often value, second key/index

Object.keys(response.data.modelState)
      .forEach(function (value, key) {
    errors.push.apply(errors, response.data.modelState[key]);
});

And even, we should use arrow function, to get the parent as this

Object.keys(response.data.modelState)
      .forEach( (value, key) => {
    errors.push.apply(errors, response.data.modelState[key]);
});

Missing an obvious answer, needed when not assigning it to a variable: [] as string[]

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