I've learned (the hard way) that I need to add parentheses around JSON data, like this:
stuff = eval('(' + data_from_the_wire + ')');
// where data_from_the_wire was, for example {"text": "hello"}
(In Firefox 3, at least).
What's the reason behind this? I hate writing code without understanding what´s behind the hood.
将括号放在data_from_the_wire左右实际上相当于
stuff = eval('return ' + data_from_the_wire + ';');
If you were to eval without the parentheses, then the code would be evaluated, and if you did have any named functions inside it those would be defined, but not returned.
以创建函数时调用函数的能力为例:
(function() { alert('whoot'); })()
Will call the function that has just been defined. The following, however, does not work:
function() { alert('whoot'); }()
因此，我们看到括号有效地将代码转换为返回的表达式，而不仅仅是要运行的代码.