How to correctly initialize vector of number in Typescript

I'm having difficulties at initializing a variable with the value returned from a function.
The function is hosted here and it should return an array of numbers.
So I try to define my variable as

import {default as linspace} from '@stdlib/array-linspace'

var xvalues:number[] = linspace(0,10, 10)

And the IDE gives me an error because Type 'Float64Array' is missing the following properties from type 'number[]': pop, push, concat, shift, and 5 more.ts(2740)
So I checked what was actually being returned by the function with the following logs:

console.log(typeof linspace(0,10,10) )
console.log(typeof linspace(0,10,10)[0] )

And the types are in fact

Object
number

Then why defining my variable as var xvalues:number[] is not correct?

The error message is telling you what type to use Float64Array:

let xvalues: Float64Array = linspace(0,10, 10)

(var shouldn't be used in new code.)

That said, there's no need for an explicit annotation, TypeScript will infer it for you:

let xvalues = linspace(0,10, 10)

> Then why defining my variable as var xvalues:number[] is not correct?

Because number[] and Float64Array are different things. It's true that a Float64Array contains number values, but it's a different container than a standard array. It's also worth noting you'd have gotten the same result logging the type of an element value from a Float32Array, an Int8Array, or any other typed array other than BigInt64Array even though the contain different kinds of numbers, because when you access a value in a typed array, it's converted from its raw type (an 8-bit two's complement number, for instance, in the case of an Int8Array) to the plain number type.