使用对象属性

 

var foo = {a: "alpha", 2: "two"};

foo[a]  -->  ReferenceError: a is not defined

foo[2]  -->  "two"

foo.a  -->  "alpha"

console.log(foo.2)  -->  SyntaxError: missing ) after argument list

foo["a"]  -->  "alpha"

foo["2"]  -->  "two"