javascript 带有对象的Javascript三元运算符

Javascript ternary operator with object

提问by lboyel

I came across a piece of code I am trying to figure out, the code basically stores the occurrence of the amount of time a word appears in a text document, so the function countWordsIntexttakes in the desired text and displays the word and the number of occurrence in the text, e.g would: 3 but: 5 very: 6

我遇到了一段我想弄清楚的代码，该代码基本上存储了一个单词在文本文档中出现的时间量，因此函数countWordsIntext接收所需的文本并显示单词和出现的次数出现在文本中，例如将：3 但：5 非常：6

while looking at the function that counts the word in the text I cant figure out how the conditional tenary operation is supposed to work. An explanation would be very much appreciated

在查看计算文本中单词的函数时，我无法弄清楚条件十进制操作应该如何工作。非常感谢解释

var wordCounts = {};

 function countWordsInText(text) {
    var words = text.toString()
                .toLowerCase()
                .split(/\W+)
                .sort();
    for(var index in words) {
    var word = words[index];
    if(word) {
     wordCounts[word] =
        (wordCounts[word]) ? wordCounts[word] + 1 : 1;
       }
   }
} 

function display()
{
  for (var index in wordCounts)
   console.log(index + ': ' + wordCounts[index]);
}

I don't understand how the wordCounts[word]object property is updated.

我不明白wordCounts[word]对象属性是如何更新的。

回答by Paul S.

Say you have

说你有

var foo = {};

The line that is confusing you would be

令你困惑的那条线

foo.bar = foo.bar ? foo.bar + 1 : 1; // line A

Ask yourself

问你自己

1. What is foo.barat the start? It is undefined, we didn't give fooa property bar
2. What is foo.barafter the first time line A is executed? It is 1; foo.barwas undefinedwhich is falsyso the ternary operator gave us back 1
3. What is foo.barafter the second time line A is executed? It is 2; foo.barwas 1which is truthy, so the ternary operator gave us back foo.bar + 1

1. 什么是foo.bar在开始？它是undefined，我们没有给出foo属性栏
2. 什么是foo.bar第一次线后执行的？它是1; foo.bar在不确定的是falsy所以三元运营商提供给我们回1
3. 什么是foo.bar第二次行之后被执行的？它是2; foo.bar是1这是truthy，所以三元运营商提供给我们回foo.bar + 1

Line A can be repeated until you run out of numbers or the world explodes

A 行可以重复，直到你用完数字或世界爆炸

Writing it like this is a way to solve the undefined + 1problem, which would give NaN

像这样写是解决undefined + 1问题的一种方法，这会给NaN

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An equally valid solution (which I find a bit cleaner to read personally) would be to do

一个同样有效的解决方案（我觉得个人阅读更清晰）是

foo.bar = (foo.bar || 0) + 1;