TS2364：赋值表达式的左侧无效

Question

a is a mutable array, so why can't I assign to it?

foo.ts

export let a: any[];

bar.ts

import {a} from './foo';

a = [5,6,7];

Answer 1

a contains a mutable array, so you can mutate it:

a.splice(0, a.length, 5, 6, 7);
console.log(a);

a in bar is an imported binding however, and those cannot be reassigned. That's why it's a syntax error.

You can assign to a in foo however, where it's just behaving like a normal variable.

Answer 2

If you want to be able to change the value of the array inside the original scope ( foo.ts ) then you can do something like:

export var a = {
    arr: []
}

and then in bar.ts :

import {a} from './foo';

a.arr = [5,6,7];