list = [
{"city":"beijing","price":22},
{"city":"shanghai","price":23},
{"city":"shenzhen","price":24},
{"city":"guangzhou","price":21}]

我想得到 一个object 类似下面这种：

myObj= {"bejing":false,
 "shanghai":false,
 "shenzhen":false,
 "guangzhou":false}

怎么样用简短的语句做个loop?
是不是用map ？要怎么用？
谢谢！

Object.fromEntries(list.map(o => [ o.city, false ]))

用循环这样写：

const myObj = {}
for (let o of list) myObj[o.city] = false