Improve var scoping/hoisting description

[domleonard]

Description

Remove ambiguity in var Description that can be construed to mean standard scripts have their own scope.

Expand the first sentence ofvar Hoisting to explicitly say that Hoisting occurs during JavaScript compilation.

Motivation

Changes to the description are aimed at preventing readers from inferring that individual scripts have "script" scope.

The change to var Hoisting is to explicitly indicate that var declarations (and hoisting) don't take effect until the script is compiled - in words that do not touch on the semantics of host environment support for separate compilation of one or more script sources.

See Issue 27966 for a case study (on Stack Overflow) involving both of these proposals.

Related Articles

• Grammar and Types > Variable Scope
• Glossary > Global Scope

Related issues and pull requests

Fixes #27966

[Josh-Cena]

I try to avoid the concept of "JavaScript compilation" because it's very ambiguous. Is it JIT? Is it realm initialization? Is it source parsing? In fact, var declarations are processed as the first step of execution, just before user-visible evaluation. See for examle: https://tc39.es/ecma262/#sec-source-text-module-record-initialize-environment

[domleonard]

The latest changes to "Description" resolve that part of the issue I was concerned about.

For Hoisting I'm happy to leave out "JavaScript Compilation" altogether. The version below changes

• the first sentence to imply "script" means lines of code within a single script source.
  
• the last sentence to not say that hoisting may move declarations to the top of global code.

---

### Hoisting

var declarations, wherever they occur in a script, are processed before any code for the script is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared. This behavior is called hoisting, as it appears that the variable declaration is moved to the top of the function, static initialization block or script source in which it occurs.

---

[Sorry about proposing the update here if it should have been done as an edit to the PR - this is my first experience of Git work flow.]

[Josh-Cena]

Suggested change

`var` declarations, wherever they occur, are processed during JavaScript compilation before any code is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared. This behavior is called [_hoisting_](/en-US/docs/Glossary/Hoisting), as it appears that the variable declaration is moved to the top of the function or global code.

`var` declarations, wherever they occur in a script, are processed before any code within the script is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared. This behavior is called [_hoisting_](/en-US/docs/Glossary/Hoisting), as it appears that the variable declaration is moved to the top of the function, static initialization block, or script source in which it occurs.

So you are proposing the change above? This is okay for me. You can click the Commit suggestion button.

[Josh-Cena]

In fact I suggest adding another note to specifically point out about multiple scripts:

Suggested change

	`var` declarations, wherever they occur, are processed during JavaScript compilation before any code is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared. This behavior is called [_hoisting_](/en-US/docs/Glossary/Hoisting), as it appears that the variable declaration is moved to the top of the function or global code.
	`var` declarations, wherever they occur in a script, are processed before any code within the script is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared. This behavior is called [_hoisting_](/en-US/docs/Glossary/Hoisting), as it appears that the variable declaration is moved to the top of the function, static initialization block, or script source in which it occurs.
	> **Note:** `var` declarations are only hoisted to the top of the current script. If you have two `<script>` elements within one HTML, the first script cannot access variables declared by the second one.

[domleonard]

I think I committed the last suggestion. And immediately noticed the note could be misconstrued to mean "ever". Here's my suggestion to clarify the note:

Note: var declarations are only hoisted to the top of the current script. If you have two <script> elements within one HTML, the first script cannot access variables declared by the second one when first executed.

[domleonard]

Or even better:

**Note: var declarations are only hoisted to the top of the current script. If you have two <script> elements within one HTML, the first script cannot access variables declared by the second before the second script has been processed and executed.

[Josh-Cena]

@domleonard Is this ready for merge?

[github-actions]

Preview URLs

• /en-US/docs/Web/JavaScript/Reference/Statements/var

(comment last updated: 2023-07-20 14:37:44)

[domleonard]

The preview looks great and I'm happy with merging it. Thank you for all the effort.

[Josh-Cena]

Great. Thank you for the nice work and congrats on your first contribution here—welcome aboard!