syscall/js: move callback helper code to misc/wasm to avoid using eval()

When using the compiled .wasm with misc/wasm/wasm_exec.js, we get an error message if the site prohibits eval() via the Content-Security-Policy header. This can be resolved by moving the callback helper code from src/syscall/js/callback.go to misc/wasm/wasm_exec.js.

Fixes #26748

Change-Id: I28f271b8a00631f4c66a1ac31305e85f20f9d420
GitHub-Last-Rev: a6a0268f38d36c198ca6b4ceb2e75cc8afec74eb
GitHub-Pull-Request: golang/go#26750
Reviewed-on: https://go-review.googlesource.com/127296
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index f3772652da..94b9552c59 100644
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -387,6 +387,28 @@
 				await callbackPromise;
 			}
 		}
+
+		static _makeCallbackHelper(id, pendingCallbacks, go) {
+			return function() {
+				pendingCallbacks.push({ id: id, args: arguments });
+				go._resolveCallbackPromise();
+			};
+		}
+
+		static _makeEventCallbackHelper(preventDefault, stopPropagation, stopImmediatePropagation, fn) {
+			return function(event) {
+				if (preventDefault) {
+					event.preventDefault();
+				}
+				if (stopPropagation) {
+					event.stopPropagation();
+				}
+				if (stopImmediatePropagation) {
+					event.stopImmediatePropagation();
+				}
+				fn(event);
+			};
+		}
 	}
 
 	if (isNodeJS) {