support for regex based name filtering

README.md

@@ -63,6 +63,7 @@ a double dash to prevent input files being used as option arguments:
                                               not used.
     -m, --mangle [options]      Mangle names/specify mangler options:
                                 `reserved`  List of names that should not be mangled.
+                                `regex` Only mangle matched identifiers.
     --mangle-props [options]    Mangle properties/specify mangler options:
                                 `builtins`  Mangle property names that overlaps
                                             with standard JavaScript globals.
@@ -219,6 +220,13 @@ comma-separated list of names.  For example:
 
 to prevent the `require`, `exports` and `$` names from being changed.
 
+If you want to mangle only the names matching a specific regex, use `regex` option.
+For example:
+
+    uglifyjs ... -m regex='/^sw/'
+
+to mangle only names that starts with `sw`
+
 ### CLI mangling property names (`--mangle-props`)
 
 **Note:** THIS WILL PROBABLY BREAK YOUR CODE.  Mangling property names
@@ -783,6 +791,9 @@ If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.u
 - `toplevel` (default `false`) -- Pass `true` to mangle names declared in the
   top level scope.
 
+- `regex` (default `null`) -- Pass a RegExp literal to only mangle names matching
+  the regular expression.
+
 Examples:
 
 ```javascript

lib/minify.js

@@ -107,7 +107,12 @@ function minify(files, options) {
                 properties: false,
                 reserved: [],
                 toplevel: false,
+                regex: null,
             }, true);
+            if (options.mangle.regex !== null &&
+                options.mangle.regex.constructor.name != "RegExp") {
+                throw "Input is not a RegExp";
+            }
             if (options.mangle.properties) {
                 if (typeof options.mangle.properties != "object") {
                     options.mangle.properties = {};

lib/scope.js

@@ -386,6 +386,7 @@ function _default_mangler_options(options) {
         keep_fnames : false,
         reserved    : [],
         toplevel    : false,
+        regex       : null,
     });
     if (!Array.isArray(options.reserved)) options.reserved = [];
     // Never mangle arguments
@@ -450,6 +451,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
 
     function mangle(def) {
         if (options.reserved.has[def.name]) return;
+        if (options.regex && !options.regex.test(def.name)) return;
         def.mangle(options);
     }
 
@@ -516,6 +518,7 @@ AST_Toplevel.DEFMETHOD("expand_names", function(options) {
         if (def.global && options.cache) return;
         if (def.unmangleable(options)) return;
         if (options.reserved.has[def.name]) return;
+        if (options.regex && !options.regex.test(def.name)) return;
         var redef = def.redefined();
         var name = redef ? redef.rename || redef.name : next_name();
         def.rename = name;

test/input/name-regex/input.js

@@ -0,0 +1,2 @@
+var foo = "asasas";
+var _startsWithThis = "dddddd";

test/input/name-regex/output.js

@@ -0,0 +1 @@
+var foo="asasas";var d="dddddd";

test/mocha/cli.js

@@ -744,4 +744,36 @@ describe("bin/uglifyjs", function() {
             done();
         }).stdin.end(code);
     });
+    it("Should work with --mangle toplevel,regex='/^_startsWith/g;'", function(done) {
+        var command = uglifyjscmd + " test/input/name-regex/input.js -m toplevel,regex='/^_startsWith/g;'";
+        exec(command, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, read("test/input/name-regex/output.js"));
+            done();
+        });
+    });
+    it("Should work without regex", function(done) {
+        var command = uglifyjscmd + " test/input/name-regex/input.js -m toplevel";
+        exec(command, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, "var d=\"asasas\";var a=\"dddddd\";\n");
+            done();
+        });
+    });
+    it("Should give error against non-regex input", function(done) {
+        var command = uglifyjscmd + " test/input/name-regex/input.js -m toplevel,regex=g";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stderr, "ERROR: Input is not a RegExp\n");
+            done();
+        });
+    });
+    it("Should give error against invalid input regex", function(done) {
+        var command = uglifyjscmd + " test/input/name-regex/input.js -m toplevel,regex=//";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(true, String(stderr).indexOf("not a supported option") != -1);
+            done();
+        });
+    });
 });