diff --git a/internal/jsutil/buf_js.go b/internal/jsutil/buf_js.go
index 5fc7068f5..af5b0c6a0 100644
--- a/internal/jsutil/buf_js.go
+++ b/internal/jsutil/buf_js.go
@@ -28,27 +28,34 @@ var (
 	// temporaryArrayBuffer is a temporary buffer used at gl.readPixels or gl.texSubImage2D.
 	// The read data is converted to Go's byte slice as soon as possible.
 	// To avoid often allocating ArrayBuffer, reuse the buffer whenever possible.
-	temporaryArrayBuffer = arrayBuffer.New(16)
+	temporaryArrayBuffer           = arrayBuffer.New(16)
+	temporaryArrayBufferByteLength = temporaryArrayBuffer.Get("byteLength")
 
 	// temporaryUint8Array is a Uint8ArrayBuffer whose underlying buffer is always temporaryArrayBuffer.
-	temporaryUint8Array = uint8Array.New(temporaryArrayBuffer)
+	temporaryUint8Array           = uint8Array.New(temporaryArrayBuffer)
+	temporaryUint8ArrayByteLength = temporaryUint8Array.Get("byteLength")
 
 	// temporaryFloat32Array is a Float32ArrayBuffer whose underlying buffer is always temporaryArrayBuffer.
-	temporaryFloat32Array = float32Array.New(temporaryArrayBuffer)
+	temporaryFloat32Array           = float32Array.New(temporaryArrayBuffer)
+	temporaryFloat32ArrayByteLength = temporaryFloat32Array.Get("byteLength")
 )
 
 func ensureTemporaryArrayBufferSize(byteLength int) {
-	if bufl := temporaryArrayBuffer.Get("byteLength").Int(); bufl < byteLength {
+	bufl := temporaryArrayBufferByteLength.Int()
+	if bufl < byteLength {
 		for bufl < byteLength {
 			bufl *= 2
 		}
 		temporaryArrayBuffer = arrayBuffer.New(bufl)
+		temporaryArrayBufferByteLength = temporaryArrayBuffer.Get("byteLength")
 	}
-	if temporaryUint8Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+	if temporaryUint8ArrayByteLength.Int() < bufl {
 		temporaryUint8Array = uint8Array.New(temporaryArrayBuffer)
+		temporaryUint8ArrayByteLength = temporaryUint8Array.Get("byteLength")
 	}
-	if temporaryFloat32Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+	if temporaryFloat32ArrayByteLength.Int() < bufl {
 		temporaryFloat32Array = float32Array.New(temporaryArrayBuffer)
+		temporaryFloat32ArrayByteLength = temporaryFloat32Array.Get("byteLength")
 	}
 }