range.ts

function range(start: number, end: number, step = 1) {
    return {
        [Symbol.iterator]() {
            return this
        },
        next() {
            if (start < end) {
                start = start + step
                return {
                    value: start,
                    end: false
                }
            }
            return {
                value: end,
                end: true
            }
        }
    }
}

// Example

for (let i of range(1, 20)) {
    console.log(i)
}