13b610be03
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Implement three missing JS operators that together unblock 57 Test262 full-suite tests (pass rate 42% → 44%): - delete: reference-aware unary operator that removes object properties, with special handling for member/computed/identifier expressions - void: unary operator that evaluates operand and returns undefined - in: binary operator that checks property existence via prototype chain, gated by allow_in flag to disambiguate from for-in loops The allow_in mechanism (with_no_in helper) prevents the parser from consuming `in` as a binary operator inside for-loop initializers, which would break for-in/for-of parsing. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
26 lines
665 B
JavaScript
26 lines
665 B
JavaScript
// own property
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console.log("x" in {x: 1}); // true
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console.log("y" in {x: 1}); // false
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// prototype property
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function Animal() {}
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Animal.prototype.legs = 4;
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var a = new Animal();
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console.log("legs" in a); // true
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console.log("wings" in a); // false
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// property with undefined value still counts
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var o = {z: undefined};
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console.log("z" in o); // true
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// function properties
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function f() {}
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f.custom = 1;
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console.log("custom" in f); // true
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console.log("missing" in f); // false
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// numeric key coercion
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var arr = [10, 20, 30];
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console.log(0 in arr); // true
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console.log(5 in arr); // false
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