如何在 JavaScript 中的数组上切换（）？

Question

我有一个空数组如下：

var itemsWithEmptySockets = [];

可能会填充以下一个或多个值（取决于通过 n API 提取的信息）：

0, 1, 2, 4, 5, 6, 7, 8, 9, 15, 16

其中：

0 = Head
1 = Neck
2 = Shoulder
4 = Chest
5 = Waist
6 = Legs
7 = Feet
8 = Wrist
9 = Hands
14 = Back
15 = MainHand
16 = SecondaryHand

我想测试看看数组中有什么，并通过将字符串存储在数组中来将这些数字转换为字符串，例如如果为 0，则 Head 有一个空套接字，将 "Head" 添加到新数组，然后我想用它来将 "Head" 显示为 DOM.[=17= 中的字符串]

为此，我尝试了一个 switch 语句，例如

switch(itemsWithEmptySockets){
case 0:
emptyItems.push("Head");
break;

然而，switch 语句似乎不支持以这种方式使用数组，即传递数组 itemsWithEmptySockets.

有没有比 12 个 if 语句更有效的方法？例如

for(i=0; i < itemsWithEmptySockets.length; i++){
    if(itemsWithEmptySockets[i] == 0){
      emptyItems.push("Head");
    }
if(itemsWithEmptySockets[i] == 1){
      emptyItems.push("Neck");
    }
etc.
}

非常感谢您的帮助！

Answer 1

我不会为此使用 switch，我不认为；我会使用映射对象：

// In one central place
var socketMappings = {
    0: "Head",
    1: "Neck",
    2: "Shoulder",
    4: "Chest",
    5: "Waist",
    6: "Legs",
    7: "Feet",
    8: "Wrist",
    9: "Hands",
    14: "Back",
    15: "MainHand",
    16: "SecondaryHand"
};

// Where you're doing this
var emptyItems = [];
itemsWithEmptySockets.forEach(function(entry) {
    emptyItems.push(socketMappings[entry]);
});

实例：

// In one central place
var socketMappings = {
  0: "Head",
  1: "Neck",
  2: "Shoulder",
  4: "Chest",
  5: "Waist",
  6: "Legs",
  7: "Feet",
  8: "Wrist",
  9: "Hands",
  14: "Back",
  15: "MainHand",
  16: "SecondaryHand"
};

// Where you're doing this
itemsWithEmptySockets = [
  0,
  14,
  5
];
var emptyItems = [];
itemsWithEmptySockets.forEach(function(entry) {
  emptyItems.push(socketMappings[entry]);
});

// Show result
snippet.log(itemsWithEmptySockets.join(", "));
snippet.log(emptyItems.join(", "));

<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

或者如果 emptyItems 中没有其他内容，请使用 Array#map:

// In one central place
var socketMappings = {
    0: "Head",
    1: "Neck",
    2: "Shoulder",
    4: "Chest",
    5: "Waist",
    6: "Legs",
    7: "Feet",
    8: "Wrist",
    9: "Hands",
    14: "Back",
    15: "MainHand",
    16: "SecondaryHand"
};

// Where you're doing this
var emptyItems = itemsWithEmptySockets.map(function(entry) {
    return socketMappings[entry];
});

实例：

// In one central place
var socketMappings = {
  0: "Head",
  1: "Neck",
  2: "Shoulder",
  4: "Chest",
  5: "Waist",
  6: "Legs",
  7: "Feet",
  8: "Wrist",
  9: "Hands",
  14: "Back",
  15: "MainHand",
  16: "SecondaryHand"
};

// Where you're doing this
itemsWithEmptySockets = [
  0,
  14,
  5
];
// Where you're doing this
var emptyItems = itemsWithEmptySockets.map(function(entry) {
  return socketMappings[entry];
});

// Show result
snippet.log(itemsWithEmptySockets.join(", "));
snippet.log(emptyItems.join(", "));

<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

Answer 2

要回答您标题中的问题，您不能。

为您的问题提出更好的解决方案。假设各种值的值始终相同，我会将其存储在 object 中：

var parts = {
    0: 'Head',
    1: 'Neck',
    // ...
    15: 'MainHand',
    16: 'SecondaryHand'
}

然后，当您想根据 api 数据填充时，请执行以下操作：

for(var i = 0; i < itemsWithEmptySockets.length; i++){
   emptyItems.push(parts[itemsWithEmptySockets[i]]);
}

您还可以动态定义部分 object，如果它也可以通过 api 检索到。

Answer 3

另一个选项是使用 Array.prototype.map 和自定义查找方法：

function BodyPartLoookup(x){
  switch (x){
    case 0: return 'Head';
    case 1: return 'Neck';
    case 2: return 'Shoulder';
    case 4: return 'Chest';
    case 5: return 'Waist';
    case 6: return 'Legs';
    case 7: return 'Feet';
    case 8: return 'Wrist';
    case 9: return 'Hands';
    case 14: return 'Back';
    case 15: return 'MainHand';
    case 16: return 'SecondaryHand';
    default: return '';
  }
}

var originalArray = [0, 1, 2, 4, 5, 6, 7, 8, 9, 15, 16];
var resolvedArray = originalArray.map(BodyPartLoookup);

document.getElementById('output').innerHTML = resolvedArray.join(', ');

<pre id="output"></pre>

Answer 4

您可以创建一个包含项目大小的数组，然后您可以在没有循环或开关的情况下索引该值。

由于这是一个很小的列表，而且索引在很小的范围内，因此创建地图似乎效率低下，但如果您的索引范围非常大，那么创建地图将是一个明智的选择。

/* Redirect console output to HTML. */ document.body.innerHTML='';
console.log=function(){document.body.innerHTML+=[].slice.apply(arguments).join(' ')+'\n';};

const BODY_PARTS = ['Head', 'Neck', 'Shoulder', null, 'Chest', 'Waist', 'Legs', 'Feet',
    'Wrist', 'Hands', null, null, null, null, 'Back', 'MainHand', 'SecondaryHand'];

var itemsWithEmptySockets = [4, 2, 6, 8, 13, 9, 3, 5];
var emptyItems = [];

for (var i = 0; i < itemsWithEmptySockets.length; i++) {
  emptyItems.push(BODY_PARTS[itemsWithEmptySockets[i]]);
}

console.log(JSON.stringify(emptyItems, null, '  '));

body { font-family: monospace; white-space: pre; }

如何在 JavaScript 中的数组上切换（）？

How do I switch() on an array in JavaScript?

javascript

arrays

switch-statement