Javascript 文字表达式

Question

“use strict” - 定义 JavaScript 代码应在严格模式下执行。

有没有其他类似"use strict";的JavaScript文字表达式？

Answer 1

目前没有，不，"use strict"; 是唯一的。

规范称这些为“指令”。它们是“指令序言”的一部分。详情 in the spec :

Directive Prologues and the Use Strict Directive

A Directive Prologue is the longest sequence of ExpressionStatement productions occurring as the initial StatementListItem or ModuleItem productions of a FunctionBody, a ScriptBody, or a ModuleBody and where each ExpressionStatement in the sequence consists entirely of a StringLiteral token followed by a semicolon. The semicolon may appear explicitly or may be inserted by automatic semicolon insertion. A Directive Prologue may be an empty sequence.

A Use Strict Directive is an ExpressionStatement in a Directive Prologue whose StringLiteral is either the exact code unit sequences "use strict" or 'use strict'. A Use Strict Directive may not contain an EscapeSequence or LineContinuation.

A Directive Prologue may contain more than one Use Strict Directive. However, an implementation may issue a warning if this occurs.