将 javascript 变量声明为特定类型
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Declaring javascript variables as specific types
提问by CBredlow
The title says it all, but I will provide more clarification:
标题说明了一切，但我将提供更多说明：
After seeing many samples of javascript where all variables are declared as type var, and seeing support for other datatypes, why aren't variables of a specific datatype declared as such? Meaning, why isn't this:
在看到所有变量都声明为 type 的许多javascript示例var并看到对其他数据类型的支持后，为什么不这样声明特定数据类型的变量？意思是，为什么不是这个：
string hello = 'Hello, World'
string hello = 'Hello, World'
used instead of
代替
var hello = 'Hello, World'
var hello = 'Hello, World'
Looking at sites like OReilly Javascriptshows that there are reserved words for other types. Again, why aren't they used? Wouldn't it make lines like this: typeof(variable)==='string';no longer needed?
看看像OReilly Javascript这样的网站，就会发现其他类型的保留字。再次，为什么不使用它们？会不会像这样：typeof(variable)==='string';不再需要？
回答by Matt Ball
Quite simply, JavaScript variables do not have types. The valueshave types.
很简单，JavaScript 变量没有类型。该值具有的类型。
The language permits us to write code like this:
该语言允许我们编写如下代码：
var foo = 42;
foo = 'the answer';
foo = function () {};
So it would be pointless to specify the type in a variable declaration, because the type is dictated by the variable's value. This fairly common in "dynamic" languages.
所以在变量声明中指定类型是没有意义的，因为类型是由变量的值决定的。这在“动态”语言中相当普遍。
