.forEach vs. for..of in TS

ts-foreach-forof.ts

let value: string | undefined
const items: any[] = []

if (value) {
    items.forEach(() => {
        // value is string | undefined
        // TS can't (and shouldn't) know whether this callback is synchronous; `value` might have changed
        value
    })

    for (const item of items) {
        // value is string
        // for..of loops are _always_ synchronous,
        // so we know for sure that it won't have changed at this point
        value
    }
}