javascript - 为什么Array.indexOf（）可以与一个redux动作一起正常工作，而不能与另一个动作一起正常工作？ （相同的减速器）(Why is Array.indexOf() working correctly with one redux action but not with another? (same reducer))

Question

var tags = ['tag1', 'tag2', 'tag3', 'tag4', 'tag5',
            'tag6', 'tag7', 'tag8', 'tag9', 'tag0'];

var selectedTags = [];

const tagsReducer = (state={}, action) => {
    var tagIndex = '';
    if(action.type==="ADD_TAG") {                     //this if statement works as expected
        tagIndex = tags.indexOf(action.payload);
        selectedTags.push(tags[tagIndex]);
        tags.splice(tagIndex, 1);
        return {tags, selectedTags};    
    }
    if(action.type==="REMOVE_TAG"){                          //this doesn't
        tagIndex = selectedTags.indexOf(action.payload);
        console.log(selectedTags);                            //prints the expected array
        console.log(action.payload);                          //prints the expected string
        console.log(tagIndex);                                //prints -1 (doesn't find the string)
        console.log(typeof(selectedTags));                    //prints object
        console.log(typeof(action.payload));                  // prints string
        tags.push(selectedTags[tagIndex]); 
        selectedTags.splice(tagIndex, 1);

        return {tags, selectedTags};
    }
    return {tags, selectedTags}
}

The string mathes one of the array items, but the indexOf() function still returns -1.

(字符串对数组项之一进行数学运算，但是indexOf（）函数仍返回-1。)

It's confusing because the first action works fine, but the second doesn't.

(这很令人困惑，因为第一个操作可以正常运行，但是第二个则不能。)

Any suggestions?

(有什么建议么？)

  ask by redmaster translate from so

Answer 1

string mathes one of the array items, but the indexOf() function still returns -1

(字符串运算是数组项之一，但是indexOf（）函数仍返回-1)

It doesn't match one of the array items as of when you're calling indexOf , because if it did, indexOf would find it.

(调用indexOf ，它与数组项之一不匹配，因为如果匹配，则indexOf会找到它。)

indexOf isn't broken .

(indexOf 没有坏 。)

So that leaves two general possibilities:

(这样就留下了两种一般可能性：)

1. The string that's in the array looks like it should match, but is slightly different from the string in the payload .

   (数组中的字符串看起来应该匹配，但与payload的字符串略有不同。)

   Ways it might be different that may not be obvious:

   (可能并不明显的不同方式：)

   • One of them (the one in the array or the one in payload ) may have a space at the beginning or end, etc.

     (其中一个（数组中的一个或payload的一个）可能在开头或结尾处都有空格，等等。)

   • One of them may have a slight difference in capitalization.

     (其中之一可能在大小写上略有不同。)

   • They may have slightly different characters that are easily confused, like ? and c? .

     (它们可能具有容易混淆的略有不同的字符，例如?和c? 。)

   • The entry in the array may have a comma in it, for instance "thisTag,thatTag" which won't, of course, match "thatTag" if you go looking, although it looks like "thatTag" is in the array.

     (数组中的条目中可能包含逗号，例如"thisTag,thatTag" ，尽管看起来像"thatTag"在数组中，但如果您去看，当然不会与"thatTag"匹配。)

   • One of them may be a String object where the other is a string primitive;

     (其中一个可以是String对象，另一个可以是字符串基元。)

     String objects and string primitives are not === to each other, and indexOf uses a === test.

     (String对象和字符串基元彼此不是=== ，并且indexOf使用===测试。)

2. The string isn't in the selectedTags array as of when you call indexOf , even though it looks like it in the console.

   (截至调用indexOf ，该字符串已不在selectedTags数组中，即使在控制台中看起来也是如此。)

   That's because of this feature of consoles .

   (这是因为consoles的这一功能 。)

To figure it out, set a breakpoint on the indexOf line and, when it's hit, look at the string in payload and the string in selectedTags (if it's there — if not, then it was the console thing).

(为了弄清楚它，在indexOf行上设置一个断点，当命中它时，查看payload的字符串和selectedTags的字符串（如果有的话-如果不是，那是控制台的事）。)

You'll find some difference.

(您会发现一些区别。)