使用javascript计算短语中每个单词的出现次数

问题描述

例如对于输入olly olly in come free"

程序应该返回:

olly: 2在:1来:1免费:1

测试写成:

var words = require('./word-count');

describe("words()", function() {
  it("counts one word", function() {
    var expectedCounts = { word: 1 };
    expect(words("word")).toEqual(expectedCounts);
  });

//more tests here
});

1. 如何从我的 word-count.js 文件开始?创建一个方法 words() 或一个模块 Words() 并在其中创建一个 expectedCount 方法并导出它?

1. How do I start in my word-count.js file? Create a method words() or a module Words() and make an expectedCount method in there and export it?

我将字符串视为数组还是对象?在对象的情况下，我如何开始将它们分解成单词并迭代计数?

Do I treat the string as an array or an object? In the case of objects, how do I start breaking them into words and iterate for the count?

推荐答案

function count(str) {
  var obj = {};
  
  str.split(" ").forEach(function(el, i, arr) {
    obj[el] = obj[el] ? ++obj[el] : 1;
  });
  
  return obj;
}

console.log(count("olly olly in come free"));

这段代码应该能得到你想要的.
为了更好地理解代码，我建议您通过数组原型函数和字符串原型函数.
为了简单了解我在这里做什么:

This code should get just what you want.
For more understanding on the code I would advice you to go through array prototype functions and string prototype functions.
For simple understanding of what I`m doing here:

1. 创建一个计数函数，该函数返回一个计数所有单词出现次数的对象.
2. 使用 split(" ") 根据提供数组的空格分割字符串.
3. 使用 forEach 方法遍历 spitted 数组中的所有元素.
4. 三元运算符 :? 检查值是否已经存在，是否加一或赋值为 1.

1. Create a count function which returns an object of count of all occurrences of words.
2. Split the string using split(" ") based on a space which gives an array.
3. Use forEach method to iterate through all the elements in the spitted array.
4. Ternary operator :? to check if value already exists, if it does increment by one or assign it to 1.

Array.prototypeString.prototype

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