eval-json-differences.js

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load(libdir + "asserts.js");

// eval({__proto__}) changes [[Prototype]]

var obj = eval('({"__proto__": null})');

assertEq(Object.getPrototypeOf(obj), null);

assertEq(Object.prototype.hasOwnProperty.call(obj, "__proto__"), false);

// JSON.parse({__proto__}) creates new property __proto__

obj = JSON.parse('{"__proto__": null}');

assertEq(Object.getPrototypeOf(obj), Object.prototype);

assertEq(Object.prototype.hasOwnProperty.call(obj, "__proto__"), true);

// If __proto__ appears more than once as quoted or unquoted property name in an

// object initializer expression, that's an error.

//(No other property name has this restriction.)"

assertThrowsInstanceOf(() =>

    eval('({ "__proto__" : null, "__proto__" : null })'), SyntaxError);

assertThrowsInstanceOf(() =>

    eval('  ({ "__proto__" : null, "__proto__" : null })'), SyntaxError);

// JSON.parse doesn't care about duplication, the last definition counts.

obj = JSON.parse('{"__proto__": null, "__proto__": 5}');

assertEq(Object.getPrototypeOf(obj), Object.prototype);

assertEq(obj["__proto__"], 5);