I simply can't understand why the second and the third lines of output differs one from another:
我简直无法理解为什么第二行和第三行的输出彼此不同：
alphabet_ASCII = '';
for (i=65; i<=90; i++) {
alphabet_ASCII += i;
}
alphabet_ASCII += '<br>';
document.body.innerHTML += alphabet_ASCII;
document.body.innerHTML +=
alphabet_ASCII.replace(/\d{2}/g, x=>String.fromCharCode(x));
document.body.innerHTML +=
alphabet_ASCII.replace(/\d{2}/g, String.fromCharCode);What's the difference between x=>String.fromCharCode(x) and String.fromCharCode?
x => String.fromCharCode（x）和String.fromCharCode之间有什么区别？
1 个解决方案
#1
6
Because String.fromCharCode accepts multiple arguments, and replace calls the callback with more than just the one argument you're expecting: It calls the callback with:
因为String.fromCharCode接受多个参数，并且替换调用回调不仅仅是你期望的一个参数：它调用回调：
- All matching text
- 所有匹配的文字
- The contents of any capture groups (if any)
- 任何捕获组的内容（如果有的话）
- The index (offset) at which this match occurred
- 发生此匹配的索引（偏移量）
- The whole string being acted on
- 整个字符串被执行
有关MDN的更多信息。
So in your second example, String.fromCharCode gets more arguments than in your first, and does its best with them. On the first callback, String.fromCharCode gets "65", 0, "6566676869707172737475767778798081828384858687888990" and so returns "A\u0000\u0000" (because the second argument is 0 and the third is invalid). On the second pass it gets "66", 2, "6566676869707172737475767778798081828384858687888990" and returns "B\u0002\u0000", etc.
所以在你的第二个例子中，String.fromCharCode获取的参数比你的第一个更多，并且最好用它们。在第一个回调中，String.fromCharCode得到“65”，0，“6566676869707172737475767778798081828384858687888990”，因此返回“A \ u0000 \ u0000”（因为第二个参数为0，第三个参数无效）。在第二次传递它得到“66”，2，“6566676869707172737475767778798081828384858687888990”并返回“B \ u0002 \ u0000”等。
#1
6
Because String.fromCharCode accepts multiple arguments, and replace calls the callback with more than just the one argument you're expecting: It calls the callback with:
因为String.fromCharCode接受多个参数，并且替换调用回调不仅仅是你期望的一个参数：它调用回调：
- All matching text
- 所有匹配的文字
- The contents of any capture groups (if any)
- 任何捕获组的内容（如果有的话）
- The index (offset) at which this match occurred
- 发生此匹配的索引（偏移量）
- The whole string being acted on
- 整个字符串被执行
有关MDN的更多信息。
So in your second example, String.fromCharCode gets more arguments than in your first, and does its best with them. On the first callback, String.fromCharCode gets "65", 0, "6566676869707172737475767778798081828384858687888990" and so returns "A\u0000\u0000" (because the second argument is 0 and the third is invalid). On the second pass it gets "66", 2, "6566676869707172737475767778798081828384858687888990" and returns "B\u0002\u0000", etc.
所以在你的第二个例子中，String.fromCharCode获取的参数比你的第一个更多，并且最好用它们。在第一个回调中，String.fromCharCode得到“65”，0，“6566676869707172737475767778798081828384858687888990”，因此返回“A \ u0000 \ u0000”（因为第二个参数为0，第三个参数无效）。在第二次传递它得到“66”，2，“6566676869707172737475767778798081828384858687888990”并返回“B \ u0002 \ u0000”等。