TypeScript casting arrays

Question

I'm trying to use a wrapper for a library that wants an Array as an input parameter.

I tried casting the Array, but I get an error: Cannot convert 'any[]' to 'Array'

Is there a way to make this work?

var rows = new Array(10);
var rows2 = <Array>rows; //<--- Cannot convert 'any[]' to 'Array'

I can convert the wrapper to any[], but I'd like to know why I can't cast to an Array. — Adam Tegen
– Adam Tegen, Commented Oct 9, 2012 at 4:13

Heretic Monkey · Accepted Answer · 2019-09-20 14:21:39Z

148

There are 4 possible conversion methods in TypeScript for arrays:

let x = []; //any[]

let y1 = x as number[];
let z1 = x as Array<number>;
let y2 = <number[]>x;
let z2 = <Array<number>>x;

The as operator's mostly designed for *.tsx files to avoid the syntax ambiguity.

edited Sep 20, 2019 at 14:21

Heretic Monkey

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answered Feb 3, 2016 at 16:09

shadeglare

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Tsvetomir Nikolov · Accepted Answer · 2016-02-03 15:10:06Z

17

I think the right syntax is:

var rows2 = <Array<any>>rows;

That's how you cast to interface Array<T>

answered Feb 3, 2016 at 15:10

Tsvetomir Nikolov

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Ryan Cavanaugh · Accepted Answer · 2012-10-09 04:33:12Z

5

I think this is just a bug - can you log an issue on the CodePlex site?

As a workaround, you can write <Array><any>rows;

answered Oct 9, 2012 at 4:33

Ryan Cavanaugh

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1 Comment

Heretic Monkey Over a year ago

Presumably the issue has been fixed. And I think you all are using GitHub now? ;)

Jayant Varshney · Accepted Answer · 2019-01-02 21:12:44Z

5

A simple solution for all types

const myArray = <MyType[]>value;

answered Jan 2, 2019 at 21:12

Jayant Varshney

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1 Comment

Maxime Krier Over a year ago

this do not work, if you console log the result , myArray is not a array of MyType elements

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