JoBoEVD/UglifyJS
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adding an imaginary "return undefined" can sometimes help

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function f() {
  if (foo) return x();
  if (!bar) return y();
}

==>

function f() {
  return foo ? x() : bar ? void 0 : y();
}
This commit is contained in:
Mihai Bazon
2012-09-14 16:26:30 +03:00
parent 924aa58060
commit 5e83e7ec17
2 changed files with 49 additions and 25 deletions
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24
lib/compress.js
View File

@@ -190,9 +190,9 @@ function Compressor(options, false_by_default) {
return MAP(statements, function(stat, i){
if (stat instanceof AST_If
&& stat.body instanceof AST_Return
&& !stat.body.value
&& !stat.alternative
&& in_lambda) {
if (!stat.body.value) {
CHANGED = true;
if (i < last) {
var rest = statements.slice(i + 1);
@@ -218,6 +218,15 @@ function Compressor(options, false_by_default) {
body: stat.condition
}).optimize(compressor);
}
} else if (i == last && last > 0
&& statements[last - 1] instanceof AST_If
&& statements[last - 1].body instanceof AST_Return
&& !statements[last - 1].alternative) {
CHANGED = true;
return MAP.splice([ stat, make_node(AST_Return, stat, {
value: make_node(AST_Undefined, stat)
})]);
}
}
if (stat instanceof AST_If
&& stat.body instanceof AST_Exit
@@ -697,7 +706,7 @@ function Compressor(options, false_by_default) {
}
});
self.walk(tw);
if (vars_found > 0 && vardecl.length > 0) {
if (vars_found > 0 && vardecl.length > 1) {
vardecl.forEach(function(v){ v.hoisted = true });
var node = make_node(AST_Var, self, {
definitions: Object.keys(vars).map(function(name){
@@ -1338,6 +1347,17 @@ function Compressor(options, false_by_default) {
return self.optimize(compressor);
});
SQUEEZE(AST_SymbolRef, function(self, compressor){
return self.optimize(compressor);
});
AST_SymbolRef.DEFMETHOD("optimize", function(compressor){
if (this.name == "undefined" && this.undeclared()) {
return make_node(AST_Undefined, this);
}
return this;
});
var ASSIGN_OPS = [ '+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&' ];
AST_Assign.DEFMETHOD("optimize", function(compressor){
if (this.operator == "="

4
lib/output.js
View File

@@ -889,6 +889,10 @@ function OutputStream(options) {
var def = self.definition();
output.print_name(def ? def.mangled_name || def.name : self.name);
});
DEFPRINT(AST_Undefined, function(self, output){
// XXX: should add more options for this
output.print("void 0");
});
DEFPRINT(AST_This, function(self, output){
output.print("this");
});