JS 对象/JSON 键通配符答案

【问题标题】：JS object/JSON key wildcardJS 对象/JSON 键通配符
【发布时间】：2021-08-06 10:27:38
【问题描述】：

我有一个从 JSON 评估的对象，如下所示：

{
    "foo %s": "bar %s",
    "Hello %s world %s.": "We have multiple %s %s."
}

使用这个对象和以下输入，我试图实现这样的目标：

foo bar -> 匹配 foo %s -> bar bar
Hello foo world bar. -> 匹配 Hello %s world %s. -> We have multiple foo bar

到目前为止，我有以下代码适用于一个 %s，并且仅当它被空格包围时。

let str = "input here";
let a = {
        "foo %s": "bar %s",
        "Hello %s world %s.": "We have multiple %s %s."
    },
    p = str.split(" "),
    result;
for (let j in p) { // loop indices
    let pp = p.map(u => u); // create local array
    pp[j] = "%s"; //replace index with %s
    if (a[pp.join(" ")]) { // check if this is in the object
        result = a[pp.join(" ")].replace("%s", p[j]); // join the array and replace %s from the result
        break;
    }
}

有什么想法或建议吗？

【问题讨论】：

标签： javascript json dictionary object

【解决方案1】：

您可以将对象转换为regular expressions，然后再转换为execute them in a call to String.prototype.replace。

单个定义的替换操作示例：

console.log('Hello foo world bar.'.replace(/^Hello (.*?) world (.*?) bar\.$/, 'We have multiple $1 $2.'))
// Output: We have multiple foo bar.

这里我们基本上匹配整个字符串 - 如果匹配模式，整个内容将被替换。

如您所见，要实现此目的，您需要将"Hello %s world %s." 转换为/^Hello (.*?) world (.*?)\.$/（(.*?) 定义一个包含任何字符的非贪婪捕获组）并将"We have multiple %s %s." 转换为@987654329 @（$x 指的是x-th 捕获组的内容）。

所以你可以有这样的功能：

function replaceTemplates (str, templates) {
  // This helper function escapes any characters which would have a special
  // meaning in the regexp otherwise. $& is the match as a whole, so it replaces
  // each of these characters with themselves prepended by a backlash.
  const escapeRegExp = s => s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
  
  for (const [template, replacement] of Object.entries(templates)) {
    // We create a regexp from the template, replacing every %s with (.*?), wrapping it
    // in ^ and $ (start/end of string) and escaping all the other special characters.
    const re = new RegExp('^' + escapeRegExp(template).replace(/%s/g, '(.*?)') + '$')
    
    if (re.test(str)) {
      // To get the correct string for the right side of the string replace method,
      // we have to replace each %s in the replacement string by $1, $2, $3 etc. and
      // also replace single $ signs by $$ because the $ has a special meaning as shown
      // above, and then we can call the actual replace and return the result. But since
      // a $ in the replacement has to be escaped as just explained, we have to write
      // FOUR $ signs to get TWO at the end.
      let i = 1 // This is used as counter in the following replacing operations for $x
      const reReplacement = replacement
        .replace(/\$/g, '$$$$')
        .replace(/%s/g, () => '$' + i++) // By using a function, we can make $x dynamic
      
      return str.replace(re, reReplacement)
    }
  }
  
  return str
}

const templates = {
  'foo %s': 'bar %s',
  'Hello %s world %s.': 'We have multiple %s %s.'
}

console.log(replaceTemplates('foo bar', templates)) // Output: bar bar
console.log(replaceTemplates('Hello foo world bar.', templates)) // Output: We have multiple foo bar.

顺便说一句：如果pp = p.map(u => u) 应该创建一个副本，我建议pp = p.slice() 或只是pp = [...p]。

【讨论】：