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transform String.charAt() to index access (#1620)

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Guarded by `unsafe` as `charAt()` can be overridden.
This commit is contained in:
Alex Lam S.L
2017-03-19 02:17:15 +08:00
committed by GitHub
parent 0489d6de64
commit 274331d0ea
2 changed files with 94 additions and 6 deletions
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22
lib/compress.js
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@@ -2656,7 +2656,7 @@ merge(Compressor.prototype, {
if (self.args.length != 1) {
return make_node(AST_Array, self, {
elements: self.args
}).transform(compressor);
}).optimize(compressor);
}
break;
case "Object":
@@ -2674,7 +2674,7 @@ merge(Compressor.prototype, {
left: self.args[0],
operator: "+",
right: make_node(AST_String, self, { value: "" })
}).transform(compressor);
}).optimize(compressor);
break;
case "Number":
if (self.args.length == 0) return make_node(AST_Number, self, {
@@ -2683,7 +2683,7 @@ merge(Compressor.prototype, {
if (self.args.length == 1) return make_node(AST_UnaryPrefix, self, {
expression: self.args[0],
operator: "+"
}).transform(compressor);
}).optimize(compressor);
case "Boolean":
if (self.args.length == 0) return make_node(AST_False, self);
if (self.args.length == 1) return make_node(AST_UnaryPrefix, self, {
@@ -2692,7 +2692,7 @@ merge(Compressor.prototype, {
operator: "!"
}),
operator: "!"
}).transform(compressor);
}).optimize(compressor);
break;
case "Function":
// new Function() => function(){}
@@ -2757,7 +2757,7 @@ merge(Compressor.prototype, {
left: make_node(AST_String, self, { value: "" }),
operator: "+",
right: exp.expression
}).transform(compressor);
}).optimize(compressor);
}
else if (exp instanceof AST_Dot && exp.expression instanceof AST_Array && exp.property == "join") EXIT: {
var separator;
@@ -2811,7 +2811,7 @@ merge(Compressor.prototype, {
left : prev,
right : el
});
}, first).transform(compressor);
}, first).optimize(compressor);
}
// need this awkward cloning to not affect original element
// best_of will decide which one to get through.
@@ -2821,6 +2821,16 @@ merge(Compressor.prototype, {
node.expression.expression.elements = elements;
return best_of(compressor, self, node);
}
else if (exp instanceof AST_Dot && exp.expression.is_string(compressor) && exp.property == "charAt") {
var arg = self.args[0];
var index = arg ? arg.evaluate(compressor) : 0;
if (index !== arg) {
return make_node(AST_Sub, exp, {
expression: exp.expression,
property: make_node_from_constant(index | 0, arg || exp)
}).optimize(compressor);
}
}
}
if (exp instanceof AST_Function) {
if (exp.body[0] instanceof AST_Return) {