有没有一种简单的方法可以使用 Javascript 创建动态变量？
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Is there an easy way to create dynamic variables with Javascript?
提问by julio
I've built a data-driven google map with different icons that get assigned to the map depending on the type of item located. So if I have 5 types of landmark, and each gets a different icon (store, library, hospital, etc.)-- what I'd like to do is generate the google icon objects dynamically. I was thinking something like this:
我已经构建了一个数据驱动的谷歌地图，其中有不同的图标，这些图标根据所在项目的类型分配给地图。因此，如果我有 5 种类型的地标，并且每种都有不同的图标（商店、图书馆、医院等）——我想做的是动态生成谷歌图标对象。我在想这样的事情：
types = array('hospital','church','library','store',etc);
var i=0;
while (i<=types.length) {
var landmark + i = new google.maps.Icon();
landmark.image = "icon" + i + ".png";
i++;
}
however, as you've probably guessed, this doesn't work. I also tried using eval, like this:
但是，正如您可能已经猜到的那样，这是行不通的。我也尝试使用 eval，如下所示：
while (i<=types.length) {
doIcon(i);
i++;
}
function doIcon(i){
eval("var landmark" + i + " = new.google.maps.Icon();");
return eval("landmark" + i);
}
but it didn't work either-- I'd appreciate any pointers on generating javascript variables dynamically. It's got to be pure js, I could do it in PHP but that's not an option here.
但它也不起作用——我很感激任何关于动态生成 javascript 变量的指针。它必须是纯 js，我可以用 PHP 来完成，但这不是这里的选择。
Thanks!
谢谢！
回答by Plynx
It's really easy to do: object["variablename"] = whatever;
这真的很容易做到： object["variablename"] = whatever;
So for example you could have an object: var Landmarks = {}and you could add to it like so: Landmarks["landmark" + i] = new google.maps.Icon();and pass it that way.
例如，您可以拥有一个 object:var Landmarks = {}并且您可以像这样添加它：Landmarks["landmark" + i] = new google.maps.Icon();并以这种方式传递它。
If you need these variables to be global(why would you?) you can access the global object directly using window.
如果您需要将这些变量设为全局变量（为什么要这样做？），您可以直接使用window.
回答by Andy E
If you're going to do it using a declared object such as Landmark["landmark" + i], you really may as well use an index array rather than an associative, it's much easier for iteration. Objects aren't really used with indexed properties because Arrays do a much better job of it:
如果您打算使用诸如 之类的声明对象来执行此操作Landmark["landmark" + i]，那么您真的还不如使用索引数组而不是关联数组，这样迭代起来要容易得多。对象并没有真正与索引属性一起使用，因为数组在这方面做得更好：
var myObj = // object version
{
"item0": "blah",
"item1": "blah"
// etc
}
var myArr = // array version
[
"blah",
"blah"
// etc
]
Much more sensible to use the array:
使用数组更明智：
landmarks = []; // new array
types = array('hospital','church','library','store',etc);
var i=0;
while (i<=types.length) {
landmarks.push(new google.maps.Icon());
landmarks[i].image = "icon" + i + ".png";
i++;
}
It makes more sense to do it that way and for...inloops on objects can get a bit messy with prototyped properties being enumerable, etc.
这样做更有意义，并且for...in对象上的循环可能会因原型属性可枚举等而变得有点混乱。
If you're trying to make a variable global, add it to the window object:
如果您尝试将变量设为全局变量，请将其添加到 window 对象中：
var myCustomVar = "landmark" + i;
window[myCustomVar] = new google.maps.Icon();
alert(landmark0);
But this would be polluting the global namespace with many unnecessary variables. So you'd still be better with an array:
但这会用许多不必要的变量污染全局命名空间。所以你仍然会更好地使用数组：
window.landmarks = [];
landmarks.push(new google.maps.Icon());
// etc...
回答by Felix
Just to answer your question directly (although please note that this is not the solution you want. Check out the other answers. This is just for documentation!), here's a copy-paste from a JavaScript console:
只是为了直接回答您的问题（尽管请注意，这不是您想要的解决方案。查看其他答案。这仅用于文档！），这是来自 JavaScript 控制台的复制粘贴：
> window["myNamedVar"] = "Hello, World!";
> console.log(myNamedVar);
"Hello, World!"
回答by leepowers
You'd be better off creating a javascript object which you can use somewhat like an associative array is used in PHP:
你最好创建一个 javascript 对象，你可以使用它有点像在 PHP 中使用的关联数组：
var types = ['hospital','church','library','store'];
var landmarks= {};
for (var i in types) {
landmarks[types[i]]= new google.maps.Icon();
landmarks[types[i]].image = "icon" + i + ".png";
}
alert(landmarks['hospital'].image); // displays "icon0.png"
回答by Alfgaar
Do you really need those variables? Can't you do with this:
你真的需要这些变量吗？你不能这样做：
var types = ['hospital','church','library','store'];
for(var i =0; i < types.length; i += 1) (new google.maps.Icon()).image = "icon" + i + ".png";
Modifications done based on comment:
根据评论所做的修改：
icon name pattern changed from icon + index + .png to icon + type + .png and saving the results of the loop.
图标名称模式从 icon + index + .png 更改为 icon + type + .png 并保存循环的结果。
types = ['hospital','church','library','store'];
var landmarks = {};
// images names are of the form icon + type + .png
function createIcon(type)
{
var icon = new google.maps.Icon();
icon.image = "icon" + type + ".png";
return icon;
}
// mapping of landamarks by type and icon
for (var i = 0, len = types.length; i < len; i++)
{
landmarks[types[i]] = createIcon(types[i]);
}
the result is : { hospital : icon, church : icon, ... }
结果是：{医院：图标，教堂：图标，...}
where icon is a google map icon that has an image attribute that is a string of the form "icon{type}.png" , e.g, iconhostpital.png, iconchurch.png.
其中 icon 是一个谷歌地图图标，它有一个图像属性，它是一个 "icon{type}.png" 形式的字符串，例如 iconhostpital.png、iconchurch.png。
To use the icons write landmarks.typewhere type is one the names in the array of types, e.g. landmarks.hospital.
要使用图标landmarks.type，请在类型数组中写入其中一个类型的名称，例如landmarks.hospital。
if the image names are of the form icon + number + .png, and the number for each type is equivalent to its index in the array replace the call createIcon(type[i]) for createIcon(i).
如果图像名称的形式为图标 + 数字 + .png，并且每种类型的数字等同于其在数组中的索引，请替换对 createIcon(i) 的调用 createIcon(type[i])。
