Question

JavaScript doesn’t care if your Strings are double-quoted "double" or single-quoted 'single'.

Every example of ECMAScript 5’s strict mode has it enabled by "use strict" in double-quotes. Can I do the following (single-quotes):

alert(function(){
  'use strict';
  return !this;
}());

This will return true if Strict mode is enabled, and false if it is not.

Answer 1

For you, without using a browser that supports strict mode:

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