From: Mihai Bazon <mihai@bazon.net>
Date: Mon, 5 Nov 2012 11:13:06 +0000 (+0200)
Subject: minor optimization
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=774f2ded9422903f082f0291ec69c7a6e2edfcaf;p=UglifyJS.git

minor optimization

for `==` or `!=` against a constant, prefer to display the constant first.
should help a bit after gzip, i.e.:

    typeof foo=="undefined"
    ^^^^^^    ^^^^^^^^^^^^^

vs:

    "undefined"==typeof foo
    ^^^^^^^^^^^^^^^^^^^     (longer sequence that could repeat)

idea stolen from closure.
---

diff --git a/lib/compress.js b/lib/compress.js
index fe212b42..5cbb31c9 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1489,21 +1489,15 @@ merge(Compressor.prototype, {
             // XXX: intentionally falling down to the next case
           case "==":
           case "!=":
-            if (self.left instanceof AST_UnaryPrefix
-                && self.left.operator == "typeof"
-                && self.right instanceof AST_String
-                && self.right.value == "undefined") {
-                if (!(self.left.expression instanceof AST_SymbolRef)
-                    || !self.left.expression.undeclared()) {
-                    self.left = self.left.expression;
-                    self.right = make_node(AST_Undefined, self.right).optimize(compressor);
-                    if (self.operator.length == 2) self.operator += "=";
-                }
+            if (self.right instanceof AST_Constant && !(self.left instanceof AST_Constant)) {
+                var tmp = self.left;
+                self.left = self.right;
+                self.right = tmp;
             }
-            else if (self.left instanceof AST_String
-                     && self.left.value == "undefined"
-                     && self.right instanceof AST_UnaryPrefix
-                     && self.right.operator == "typeof") {
+            if (self.left instanceof AST_String
+                && self.left.value == "undefined"
+                && self.right instanceof AST_UnaryPrefix
+                && self.right.operator == "typeof") {
                 if (!(self.right.expression instanceof AST_SymbolRef)
                     || !self.right.expression.undeclared()) {
                     self.left = self.right.expression;