1 2var a = 10;3 4var Bar = (function() { 5 console.log(a); //undefine 6 var a = 20; 7 return function() { a += 1; console.log(a); }; 8})();9 Bar();10 Bar();11
所以,函数表达式、变量 声明他们的默认值都是 undefined.
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