小编Sai*_*hav的帖子

var developers = [
    { name: "Joe", age: 23 ,overallLevel: "high"},
    { name: "Sue", age: 28 ,overallLevel: "advanced" },
    { name: "Jon", age: 32 ,overallLevel: "high" },
    { name: "Bob", age: 24 ,overallLevel: "high" },
    { name: "Bob", age: 20 ,overallLevel: "advanced" }
]

使用array.reduce()需要在提到的数组中计算overallLevel [high:3,advanced:2]