Question

156

How can I make an empty string array in Typescript?

rated 0 times [ 159] [ 3] / answers: 1 / hits: 73792 / 9 Years ago, wed, september 23, 2015, 12:00:00

I would like to have an array that holds string error messages. Here's the code that I came up with:

var errors: [string];

errors = [];

Object.keys(response.data.modelState).forEach(function (key) {

    errors.push.apply(errors, response.data.modelState[key]);

});

I tried some different ways to add a typescript definition to the variable errors but none seem to work for this case. The first definition works okay but then when I am pushing values I need to push to an array and when I set:

errors = [];

Then it gives me an error message:

Severity Code Description Project File Line Error TS2322 Type
'undefined[]' is not assignable to type '[string]'. Property '0' is
missing in type 'undefined[]'.
Severity Code Description Project File Line Error Build: Type
'undefined[]' is not assignable to type '[string]'.

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harleyterryp

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answered 9 Years ago johnnaj · Accepted Answer

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]);

});