如何通过JavaScript循环自动生成指定结构的params参数对象

问题背景 #

我不太熟悉JavaScript，目前我编写的代码如下：

var data = [{"Column":"","keyw":"","Column_3":"day of march 2011 to someother numeric"}, {"Column":"","keyw":"","Column_3":"this 22nd day of march 2011 to someother string"}, {"Column":"","keyw":"","Column_3":"this 22nd day of march 2021 monitor ground fort ord 1990 101"}, {"Column":"","keyw":"forhidden","Column_3":" area to aoid someother douling"}, {"Column":"","keyw":"forhidden","Column_3":" area to aoid someother string forbidden area"}, {"Column":"","keyw":"notpermitted","Column_3":"y of march 2001 monitor ground not permitted in states 1990 101"}, {"Column":"forhidden area to ","keyw":"aoid","Column_3":" someother douling"}, {"Column":"forhidden area to ","keyw":"aoid","Column_3":" someother string forbidden area"}, {"Column":"forhidden area to aoid someother ","keyw":"douling","Column_3":""}, {"Column":"this 22nd day of march 2001 ","keyw":"douling","Column_3":" ground fort ord 1990 101"}];
var json = JSON.parse(JSON.stringify(data));
//var json = JSON.stringify(data);

当前我需要手动创建如下格式的params参数对象：

params = {
  a: json[0].Column,
  aa: json[0].keyw,
  aaa: json[0].Column_3,
  b: json[1].Column,
  bb: json[1].keyw,
  bbb: json[1].Column_3,
  ……
}

请问是否可以通过循环或自动化的方式实现这一参数对象的创建？

解决方案 #

当然可以！完全不用手动逐个编写键值对，通过循环就能轻松搞定这个需求。先拆解下你的需求规律：

• 数组里第i个元素（从0开始数）对应的键名，是按a、b、c...的字母序列，分别生成单个字母、两个相同字母、三个相同字母的格式
• 这三个键分别对应元素的Column、keyw、Column_3属性

基于这个规律，直接上实现代码：

var data = [{"Column":"","keyw":"","Column_3":"day of march 2011 to someother numeric"}, {"Column":"","keyw":"","Column_3":"this 22nd day of march 2011 to someother string"}, {"Column":"","keyw":"","Column_3":"this 22nd day of march 2021 monitor ground fort ord 1990 101"}, {"Column":"","keyw":"forhidden","Column_3":" area to aoid someother douling"}, {"Column":"","keyw":"forhidden","Column_3":" area to aoid someother string forbidden area"}, {"Column":"","keyw":"notpermitted","Column_3":"y of march 2001 monitor ground not permitted in states 1990 101"}, {"Column":"forhidden area to ","keyw":"aoid","Column_3":" someother douling"}, {"Column":"forhidden area to ","keyw":"aoid","Column_3":" someother string forbidden area"}, {"Column":"forhidden area to aoid someother ","keyw":"douling","Column_3":""}, {"Column":"this 22nd day of march 2001 ","keyw":"douling","Column_3":" ground fort ord 1990 101"}];
var json = JSON.parse(JSON.stringify(data));

// 初始化空的params对象
const params = {};

// 遍历数组自动生成键值对
json.forEach((item, index) => {
  // 根据索引生成对应字母：0→a，1→b，2→c...（a的ASCII码是97）
  const baseLetter = String.fromCharCode(97 + index);
  // 给params添加三个对应属性
  params[baseLetter] = item.Column;
  params[baseLetter.repeat(2)] = item.keyw;
  params[baseLetter.repeat(3)] = item.Column_3;
});

console.log(params);

代码细节说明 #

1. String.fromCharCode(97 + index)：借助ASCII码规则生成字母序列，索引0对应a，索引1对应b，以此类推
2. baseLetter.repeat(n)：快速生成重复n次的字母字符串，比如a.repeat(2)得到aa，b.repeat(3)得到bbb
3. forEach循环：自动遍历数组里的每个元素，给params对象添加对应键值对，不管数组有多少元素都能适配

小扩展 #

如果你的数组元素数量超过26个（超过字母z），String.fromCharCode会生成其他ASCII字符。要是需要处理这种场景，可以改成a1/aa1/aaa1、a2/aa2/aaa2这类键名格式，只需要调整baseLetter的生成逻辑就行，比如：

const baseLetter = `a${index + 1}`;

内容的提问来源于stack exchange，提问作者Yoyobrojo