全局let变量存储在哪里? [英] Where are global let variables stored?

问题描述

我已经在全局范围内创建了一个导航器变量，并使用let关键字为其分配了一个字符串.

I have created a navigator variable in global scope and assign it a string using let keyword.

// in a browser
    let navigator = "Hello!";
    console.log(navigator );                       // "Hello!"
    console.log(window.navigator === navigator );  // false

此处let navigator值遮盖了window.navigator.但是我很好奇let navigator到底存储在哪里?

Here let navigator value shadows the window.navigator. But I am very curious to know where exactly the let navigator gets stored in?

推荐答案

由于您使用的是let而不是var，因此它将存储在声明性的

Because you used let rather than var, it gets stored in the declarative environment record associated with the global lexical environment object, rather than on the global object itself. Environment records and lexical environment objects are specification mechanisms and not directly accessible in code (and thus the actual implementations of them can vary depending on JavaScript engine).

这是一个概念—不是全局对象属性的全局变量是从ES2015开始引入的新事物；在此之前，所有全局变量都是全局对象的属性.从ES2015开始，全局级别的let，const和class标识符绑定不保存在全局对象上，而是保存在单独的声明性环境记录上.

This is a concept — globals that aren't properties of the global object — is a new thing introduced as of ES2015; until then, all globals were properties of the global object. As of ES2015, global-level let, const, and class identifier bindings are not held on the global object, but instead on a separate declarative environment record.

环境记录和词法环境对象是用于在函数中存储局部变量的相同机制(在ES2015 +和ES5及更早版本中).

Environment records and lexical environment objects are the same mechanisms used (both in ES2015+ and in ES5 and earlier) for storing local variables within a function.

此方面的全局方面在§8.2中定义.3-SetGlobalRealmObject ，它依次引用 §8.1.2.5-NewGlobalEnvironment(G，thisValue).

The global aspect of this is defined in §8.2.3 - SetGlobalRealmObject, which in turn references §8.1.2.5 - NewGlobalEnvironment(G, thisValue).

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