misc/wasm: enable ECMAScript strict mode

Current wasm_exec.js does not enable ECMAScript strict mode. But it is
recommended to be enabled because it

1. eliminates some ECMAScript silent errors by changing them to throw
   errors
2. fixes mistakes that make it difficult for JavaScript engines to
   perform optimizations
3. prohibits some syntax likely to be defined in future versions of
   ECMAScript

This commit enables ECMAScript strict mode in wasm_exec.js following the
transition guide:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode/Transitioning_to_strict_mode

Fixes #47116

Change-Id: Ib8ffceee37e9127698fb51304241f1e429efe83e
Reviewed-on: https://go-review.googlesource.com/c/go/+/334269
Reviewed-by: Richard Musiol <neelance@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: Richard Musiol <neelance@gmail.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index 231185a123ed12f8bc6b2ad7a56a00e3615a656a..22b19fbe8095396d848e6f500b44c1bffee5b93e 100644 (file)
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -1,6 +1,7 @@
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
+"use strict";
 
 (() => {
        // Map multiple JavaScript environments to a single common API,