1const range = {  
2  start: 1,  
3  end: 5,  
4
5  [Symbol.iterator]() {  
6    let current = this.start;  
7    const end = this.end;  
8    return {  
9      next() {  
10        if (current <= end) {  
11          return { value: current++, done: false };  
12        }  
13        return { done: true };  
14      },  
15    };  
16  },  
17};  
18
19for (const num of range) {  
20  console.log(num);  
21}