如何在javascript中转换数据格式

Question

我正在尝试获取一个段落并将其转换为单词并实现每个单词的频率。

var pattern = /\w+/g,
  string = "mahan mahan mahan yes yes no",
  matchedWords = string.match(pattern);

/* The Array.prototype.reduce method assists us in producing a single value from an
   array. In this case, we're going to use it to output an object with results. */
var counts = matchedWords.reduce(function(stats, word) {

  /* `stats` is the object that we'll be building up over time.
     `word` is each individual entry in the `matchedWords` array */
  if (stats.hasOwnProperty(word)) {
    /* `stats` already has an entry for the current `word`.
       As a result, let's increment the count for that `word`. */
    stats[word] = stats[word] + 1;
  } else {
    /* `stats` does not yet have an entry for the current `word`.
       As a result, let's add a new entry, and set count to 1. */
    stats[word] = 1;
  }

  /* Because we are building up `stats` over numerous iterations,
     we need to return it for the next pass to modify it. */
  return stats;

}, {})

var dict = []; // create an empty array
// this for loop makes a dictionary for you
for (i in counts) {
  dict.push({
    'text': i
  });
  dict.push({
    'size': counts[i]
  });

};

/* lets print and see if you can solve your problem */
console.log(dict);

dict 变量返回：

[ { text: 'mahan' },{ size: 3 },{ text: 'yes' },{ size: 2 },{ text:'no'},{ size: 1 } ]

但我使用的是数据可视化代码，我需要将结果变成这样的：

[ { "text": "mahan" , "size": 3 },{ "text: "yes", size: 2 },{ "text":'no', "size": 1 } ]

我知道这是基本的，但我只是一个试图为项目使用一些代码的艺术家。感谢您的帮助。

Answer 1

简单地做：

dict.push({'text':i, "size": counts[i]});

Answer 2

您的问题是您要在数组中推送两个不同的对象，以解决您只需要推送一个对象，如 cmets 中所述。

您可以在Object.keys(counts) 上使用.map() 以更好的方式来代替for loop：

var dict = Object.keys(counts).map(function(k){
    return {text: k, size: counts[k]};
});

演示：

var pattern = /\w+/g,
    string = "mahan mahan mahan yes yes no",
    matchedWords = string.match( pattern );

var counts = matchedWords.reduce(function ( stats, word ) {
    if ( stats.hasOwnProperty( word ) ) {
        stats[ word ] = stats[ word ] + 1;
    } else {
        stats[ word ] = 1;
    }
    return stats;
}, {})


var dict = Object.keys(counts).map(function(k){
    return {text: k, size: counts[k]};
});

console.log(dict);

Answer 3

您还可以并行构建哈希表（作为 Map）和生成的数组，这可能会更快：

let pattern = /\w+/g,
  string = "mahan mahan mahan yes yes no",
  matchedWords = string.match(pattern);

let hash = new Map(), result = [];

matchedWords.forEach( word => {
  if(hash.has(word)){
    hash.get(word).size++;
  }else{
    var tmp = { text: word, size: 1};
    hash.set(word,tmp);
    result.push(tmp);
  }
});

Try it

Answer 4

每次迭代都推送两个对象。不要那样做。要修复您的代码，请执行@asdf_enel_hak 建议的in his answer，如果您想简化代码，您可以更轻松地使用更少的代码。

let pattern = /\w+/g,
  string = "mahan mahan mahan yes yes no",
  matchedWords = string.match(pattern);

let res1 = [...matchedWords.reduce((a, b) => a.set(b, (a.get(b) || 0) + 1), new Map)].map(e => ({
  text: e[0],
  size: e[1]
}));

console.log(res1);

Answer 5

这与实际问题相当相切，但是您可以将其浓缩很多。下面的例子基本上和刚刚压缩的一样，我使用了Tagged Template Literal 来增加一些额外的语法糖。

const frequency = s => s[0].match(/\w+/g).reduce((m, e) => ((m[e]=(m[e]||0)+1),m), {});

console.log(frequency`
Hello foo bar world!
Hello zoo bar world!
Hello foo car world!
Hello foo bar forld!
`);