关于javascript的交换案例 [英] Swap Case on javascript

问题描述

我创建了一个更改案例的脚本，但在文本上使用它的结果完全相同，没有一个更改。有人能解释一下吗？

I made a script that changes the case, but result from using it on text is exactly the same text, without a single change. Can someone explain this?

var swapCase = function(letters){
    for(var i = 0; i<letters.length; i++){
        if(letters[i] === letters[i].toLowerCase()){
            letters[i] = letters[i].toUpperCase();
        }else {
            letters[i] = letters[i].toLowerCase();
        }
    }
   console.log(letters);
}

var text = 'So, today we have REALLY good day';

swapCase(text);

推荐答案

像Ian所说，你需要建立一个新的字符串。

Like Ian said, you need to build a new string.

var swapCase = function(letters){
    var newLetters = "";
    for(var i = 0; i<letters.length; i++){
        if(letters[i] === letters[i].toLowerCase()){
            newLetters += letters[i].toUpperCase();
        }else {
            newLetters += letters[i].toLowerCase();
        }
    }
    console.log(newLetters);
    return newLetters;
}

var text = 'So, today we have REALLY good day';

var swappedText = swapCase(text); // "sO, TODAY WE HAVE really GOOD DAY"

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