Typescript error "Cannot find name"

Question

I am trying to use the big.js library, whose definition is here.

Now, this line works:

const CONSTANT_1 = new Big(0);

Whilst this line:

const CONSTANT_2 : Big = new Big(0);

causes the error:

error TS2304: Cannot find name 'Big'.

What's the problem?

David Sherret · Accepted Answer · 2016-07-21 18:14:35Z

4

Look at what the first one is implicitly typed as:

Problem

The reason that this doesn't work...

const CONSTANT_2: Big = new Big(0);

...is because Big is defined as a variable in the definition file—not a type:

declare var Big: BigJsLibrary.BigJS;

Solution

If you wish to use explicit typing then you need to reference the created type of the constructor...

const CONSTANT_2: BigJsLibrary.BigJS = new Big(0);

...as is shown in the definition file here:

interface BigJS_Constructors {
    new (value: number): BigJS;
    // etc...
}

answered Jul 21, 2016 at 18:06

David Sherret

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2 Comments

That works, but looks weird. Is there a way to change the .d.ts to use Big like I did?

@Elena add this statement type Big = BigJsLibrary.BigJS;