JS: minify template literals, fixes #529

js/js.go

@@ -1139,10 +1139,10 @@ func (m *jsMinifier) minifyExpr(i js.IExpr, prec js.OpPrec) {
 		parentInFor := m.inFor
 		m.inFor = false
 		for _, item := range expr.List {
-			m.write(item.Value)
+			m.write(replaceEscapes(item.Value, '`', 1, 2))
 			m.minifyExpr(item.Expr, js.OpExpr)
 		}
-		m.write(expr.Tail)
+		m.write(replaceEscapes(expr.Tail, '`', 1, 1))
 		m.inFor = parentInFor
 	case *js.NewExpr:
 		if expr.Args == nil && js.OpLHS < prec && prec != js.OpNew {

js/js_test.go

@@ -164,6 +164,7 @@ func TestJS(t *testing.T) {
 		{`0,"\"\"a'"`, "0,`\"\"a'`"},
 		{`0,"'" + '"'`, "0,`'\"`"},
 		{`0,'"' + "'"`, "0,`\"'`"},
+		{"0,`\\n\\'\\$`", "0,`\n'\\$`"},
 		{`0,"a"+"b"+5`, `0,"ab"+5`},
 		{`0,5+"a"+"b"`, `0,5+"ab"`},
 		{`0,"a"+"b"+5+"c"+"d"`, `0,"ab"+5+"cd"`},

js/util.go

@@ -970,10 +970,15 @@ func minifyString(b []byte, allowTemplate bool) []byte {
 	b[0] = quote
 	b[len(b)-1] = quote
 
+	// strip unnecessary escapes
+	return replaceEscapes(b, quote, 1, 1)
+}
+
+func replaceEscapes(b []byte, quote byte, prefix, suffix int) []byte {
 	// strip unnecessary escapes
 	j := 0
 	start := 0
-	for i := 1; i < len(b)-1; i++ {
+	for i := prefix; i < len(b)-suffix; i++ {
 		if c := b[i]; c == '\\' {
 			c = b[i+1]
 			if c == quote || c == '\\' || c == 'u' || c == '0' && (i+2 == len(b)-1 || b[i+2] < '0' || '7' < b[i+2]) || quote != '`' && (c == 'n' || c == 'r') {