var json = {'name':'zhangsan', '年龄':23, 404:'你可能迷路了'};

with(json) {
  console.log(name);//输出:zhangsan
  console.log(年龄);//输出:23
  console.log(404);//输出:404,用这种方法读取key是数字的属性,有问题
}

console.log(json.name);//输出:zhangsan
//key是中文也是支持的
console.log(json.年龄);//输出:23
//key是Number类型或者String类型的数字都不能这么读取
console.log(json.404);//报错

console.log(json['name']);/输出:zhangsan
console.log(json['年龄']);//输出:23
console.log(json['404']);//输出:你可能迷路了
json[key]
console.log(json[name]);/输出:undefinded
console.log(json[年龄]);//报错
console.log(json[404]);//输出:你可能迷路了

var jsonArr = [
  {"id": "1", "name": "A1"},
  {"id": "2", "name": "A2"},
  {"id": "3", "name": "A3"},
  {"id": "4", "name": "A4"},
  {"id": "5", "name": "A5"}
]

//创建一个查找表函数
function createLookMap(field) {
  var map = {};//创建一个空的json对象
  for (var i = 0; i < jsonArr.length; i++) {
    var value = jsonArr[i];//将数组中的元素作为json对象的值
    var key = value[field];//选取一个属性作为新的json对象的key
    map[key] = value;
  }
  return map;
}