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change undefined == x to null == x (#2882)

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fixes #2871
This commit is contained in:
Dan
2018-02-05 08:00:23 +01:00
committed by Alex Lam S.L
parent 3026bd8975
commit 9637f51b68
2 changed files with 43 additions and 1 deletions
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7
lib/compress.js
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@@ -4790,6 +4790,7 @@ merge(Compressor.prototype, {
if (compressor.option("comparisons")) switch (self.operator) {
case "===":
case "!==":
var is_strict_comparison = true;
if ((self.left.is_string(compressor) && self.right.is_string(compressor)) ||
(self.left.is_number(compressor) && self.right.is_number(compressor)) ||
(self.left.is_boolean() && self.right.is_boolean()) ||
@@ -4799,8 +4800,12 @@ merge(Compressor.prototype, {
// XXX: intentionally falling down to the next case
case "==":
case "!=":
// void 0 == x => null == x
if (!is_strict_comparison && is_undefined(self.left, compressor)) {
self.left = make_node(AST_Null, self.left);
}
// "undefined" == typeof x => undefined === x
if (compressor.option("typeofs")
else if (compressor.option("typeofs")
&& self.left instanceof AST_String
&& self.left.value == "undefined"
&& self.right instanceof AST_UnaryPrefix