是否使用 let 或 const 提升了声明的变量?

The difference between var/function/function* declarations and let/const/class declara­tions is the initialisation.
The former are initialised with undefined or the (generator) function right when the binding is created at the top of the scope. The lexically declared variables however stay uninitialised. This means that a ReferenceError exception is thrown when you try to access it. It will only get initialised when the let/const/class statement is evaluated, everything before (above) that is called the temporal dead zone.

x = y = "global";
(function() {
    x; // undefined
    y; // Reference error: y is not defined

    var x = "local";
    let y = "local";
}());

请注意，let y; 语句使用 undefined 初始化变量，就像 let y = undefined; 一样.

Notice that a let y; statement initialises the variable with undefined like let y = undefined; would have.

时间死区不是句法位置，而是变量(范围)创建和初始化之间的时间.只要不执行该代码(例如函数体或简单的死代码)，在声明上方的代码中引用变量就不是错误，并且如果您在初始化之前访问该变量，即使访问该变量也会引发异常代码位于声明下方(例如，在过早调用的提升函数声明中).

The temporal dead zone is not a syntactic location, but rather the time between the variable (scope) creation and the initialisation. It's not an error to reference the variable in code above the declaration as long as that code is not executed (e.g. a function body or simply dead code), and it will throw an exception if you access the variable before the initialisation even if the accessing code is below the declaration (e.g. in a hoisted function declaration that is called too early).

let和const在这件事上有什么区别吗?

Is there any difference between let and const in this matter?

不，就提升而言，它们的工作方式相同.它们之间的唯一区别是 constant 必须并且只能在声明的初始化部分中赋值(const one = 1;，两者都是 constone; 和以后的重新分配，如 one = 2 无效).

No, they work the same as far as hoisting is regarded. The only difference between them is that a constant must be and can only be assigned in the initialiser part of the declaration (const one = 1;, both const one; and later reassignments like one = 2 are invalid).

_{1:当然，var 声明仍然只在函数级别起作用}

_{1: var declarations are still working only on the function level, of course}

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