`new Image()` 和 `document.createElement('img')` 之间有区别吗? [英] Is there a difference between `new Image()` and `document.createElement('img')`?

问题描述

在javascript中，我可以:

In javascript, I can do:

img1 = new Image();
img2 = document.createElement('img');

我的问题是，这两种方法有区别吗?我在某处读到 Image、Form 和 Element 被称为 宿主对象，这是真的吗?如果是，什么是宿主对象?

my question is, is there a difference between the two approach? I've read somewhere that Image, Form, and Element is called host objects, is this true? If it is, what are host objects?

哪种方法更可取?

推荐答案

我找不到任何详细的参考资料，但基于 MDC - HTMLImageElement 示例，似乎 Image 是 DOM 级别 0 的一部分，而文档.createElement 是 DOM 级别 2 的一部分.

I couldn't find any detailed reference but based on the comment in the MDC - HTMLImageElement example, it seems that Image is part of DOM level 0 whereas document.createElement is part of DOM level 2.

DOM level 0 是由 Netscape 发明的，它提供了一种访问网站某些元素的方法.基本上所有浏览器都支持它以向后兼容.
但老实说，我不明白为什么 Image 构造函数存在于那里，因为据我所知，没有办法操纵 DOM 级别为 0 的文档.也许它只是在浏览器内部用于创建对象.

DOM level 0 was invented by Netscape and provided a way to access the certain elements of the website. Basically all browsers support it for backwards compatibility.
But to be honest, I don't understand why the Image constructor exists there, because, as far as I understood it, there was no way to manipulate the document with DOM level 0. Maybe it was only used internally by the browser to create the objects.

DOM level 2 是 W3C 制定的官方标准.

DOM level 2 is an official standard developed by the W3C.

有关 DOM 级别的更多信息，请查看 quirksmode.org -0 级 DOM 和 维基百科.

For more information about the DOM levels, have a look at at quirksmode.org - Level 0 DOM and Wikipedia.

我在某处读到Image、Form 和Element 被称为宿主对象，这是真的吗?

I've read somewhere that Image, Form, and Element is called host objects, is this true?

是的.

如果是，宿主对象是什么?

If it is, what are host objects?

ECMAScript 规范以这种方式激励宿主对象:

The ECMAScript specification motivates host objects this way:

ECMAScript 是一种面向对象的编程语言，用于在宿主环境中执行计算和操作计算对象.此处定义的 ECMAScript 并非旨在计算自给自足；实际上，本规范中没有关于外部数据输入或计算结果输出的规定.相反，期望 ECMAScript 程序的计算环境不仅会提供本规范中描述的对象和其他设施，还会提供某些特定于环境的宿主对象，这些对象的描述和行为超出本规范的范围，除非表明它们可能提供某些可以访问的属性和可以从 ECMAScript 程序调用的某些函数.

ECMAScript is an object-oriented programming language for performing computations and manipulating computational objects within a host environment. ECMAScript as defined here is not intended to be computationally self-sufficient; indeed, there are no provisions in this specification for input of external data or output of computed results. Instead, it is expected that the computational environment of an ECMAScript program will provide not only the objects and other facilities described in this specification but also certain environment-specific host objects, whose description and behaviour are beyond the scope of this specification except to indicate that they may provide certain properties that can be accessed and certain functions that can be called from an ECMAScript program.

和

宿主对象
宿主环境提供的对象，完成ECMAScript的执行环境.
注意任何非本机对象都是宿主对象.

host object
object supplied by the host environment to complete the execution environment of ECMAScript.
NOTE Any object that is not native is a host object.

因此，任何未在规范中定义并由环境提供的对象都是宿主对象.例如在浏览器中(以及其他):window、document 和 console.

So any object that is not defined in the specification and provided by the environment is a host object. These are for example in a browser (among others): window, document and console.

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