将javascript变量声明为特定类型 [英] Declaring javascript variables as specific types

问题描述

标题说明了一切，但我会提供更多说明：

The title says it all, but I will provide more clarification:

看到许多javascript样本后，所有变量都被声明为类型 var ，并且看到对其他数据类型的支持，为什么不声明这样的特定数据类型的变量？意思是，为什么不是这个：

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:

string hello ='Hello，World'

用于代替

var hello ='Hello，World'

查看 OReilly Javascript 显示其他类型的保留字。再次，为什么不使用它们？不会这样行： typeof（变量）==='string'; 不再需要？

Looking at sites like OReilly Javascript shows 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?

推荐答案

很简单，JavaScript变量没有类型。 值有类型。

Quite simply, JavaScript variables do not have types. The values have types.

该语言允许我们编写如下代码：

The language permits us to write code like this:

var foo = 42;
foo = 'the answer';
foo = function () {};

因此，在变量声明中指定类型是没有意义的，因为类型由变量的值。这在动态语言中相当常见。

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.

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