ECMAScript multiple Prologue Directives

Question

Certain ECMAScript environments permit switiching into a special mode by means of a Directive Prologue. ECMAScript 5 has \"use strict\" and others such as asm have their own

Answer 1

What is the correct way to construct a Directive Prologue with multiple Directives?

As the spec you linked says,

a Directive Prologue is the longest sequence of ExpressionStatement productions occurring [at the begin of a script or function] and where each [of them] consists entirely of a StringLiteral.

So you can just string them together, every of these string-literal-statements is a Directive; and can have an implementation-specific meaning (only the Use-Strict-Directive is specified). Your hunch is correct, this should work:

"use bar"
"use strict"; 'use x';
'use foo';