如何把forEach循环改成for循环

Question

如何把下面forEach循环改成for循环：

v.cityData.forEach(function(e) {
        let name = e.name.substr(0, 1);
        let len = e.cities.length;
        v.anchorMap[name] = y;
        y -= titleHeight + len * itemHeight;
      });

Answer 1

for(let i = 0; i < v.cityData.length; i++) {
    let e = v.cityData[i]
    let name = e.name.substr(0, 1);
    let len = e.cities.length;
    v.anchorMap[name] = y;
    y -= titleHeight + len * itemHeight;
}

回答完这个问题之后有种难以言表的心情。。。

Answer 2

for (let i = 0, iLen = v.cityData.length; i < iLen; i++) {
        let e = v.cityData[i];
        let name = e.name.substr(0, 1);
        let len = e.cities.length;
        v.anchorMap[name] = y;
        y -= titleHeight + len * itemHeight;
}

Answer 3

for(let e of v.cityData) {
    let name = e.name.substr(0, 1);
    let len = e.cities.length;
    v.anchorMap[name] = y;
    y -= titleHeight + len * itemHeight;
}