ES.next the corner cases
uninitializedãªçŠ¶æ…‹ã‚’æŒãŸãªã„ãŸã‚ BNF見るã ã‘ã§ã¯, initializerãªãã¦ã‚‚è¡Œã‘ãã†ã§ã™ãŒ ES6 draft仕様ã®ç‰¹å¾´ BNFã ã‘ã˜ã‚ƒãªãã¦, semanticsも見ãªã‘ã‚Œã°ã„ã‘ãªã„よã†ã«ãªã£ãŸ section 12.2.1 Static Semantics LexicalBinding : BindingIdentifier It is a Syntax Error if the BindingIdentifier if IsConstantDeclaration of the LexicalDeclaration containing this production is true.
Proxyã§ã‚ªãƒ–ジェクトã«length - ã¶ã‚Œã™ã¨ã¤ãƒ¼ã‚‹
ã‚ã‚‹æ—¥ã€ä¼šç¤¾ã§ã€Œã‚ªãƒ–ジェクトã«lengthプãƒãƒ‘ティãŒæ¬²ã—ã„ã€ã¨ã„ã‚ã‚ŒãŸã®ã§è‰²ã€…考ãˆã¦ã¿ã¾ã—ãŸã€‚。 lengthプãƒãƒ‘ティã¯Arrayオブジェクトã¨ã‹ã«å˜åœ¨ã™ã‚‹ã‚ã‚Œã§ã™ã€‚ var ary = ["a", "b", "c"]; console.log(ary.length); // output: 3 ã“れを普通ã®ã‚ªãƒ–ジェクトã«ã‚‚欲ã—ã„ã¨ã„ã‚ã‚Œã¾ã—ãŸã€‚ ç†æƒ³ã¯ã“ã‚“ãªæ„Ÿã˜ã‚‰ã—ã„。 /* error */ var obj = { 'a': 1, 'b': 2, 'c': 3 }; console.log(obj.length); // output: 3 ã¦ã£ã¨ã‚Šã°ã‚„ã関数化ã™ã‚‹ã¨ã“ã‚“ãªæ„Ÿã˜ã€‚ Object.prototype.length = function () { var i = 0, prop; for (prop in this) { if (this.hasOwnProperty(
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