请问怎么将javascript中的一个字符串转化为二维数组？

polylines:
[
{id:"transit_leg_0_0",group:"walk",points:"qnnsFwy_eUvBzCPd@",levels:"B?B",numLevels:4,zoomFactor:16},
{id:"transit_leg_0_1",group:"walk",points:"gjnsFus_eU`AXxAAvFkEAE",levels:"B???B",numLevels:4,zoomFactor:16},
{id:"transit_leg_0_4",group:"walk",points:"w|zrF{nxeU\\`@bGeK",levels:"B?B",numLevels:4,zoomFactor:16},{id:"transit_leg_0_5",group:"walk",points:"uszrF_zxeUgAqAeFrI",levels:"B@B",numLevels:4,zoomFactor:16},
{id:"transit_leg_0_6",group:"walk",points:"c}zrF}qxeUc@J}BbE_@TWE",levels:"B???B",numLevels:4,zoomFactor:16}
]

比如说将[]之间的字符串转化为一个二维数组，怎么弄？
一维的我弄过，用eval就搞定了，但是二维的就出错了，请大侠帮忙阿！！！

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小弟我新手，最好给出实际的代码！谢谢！

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这个搞二维干嘛？没有意义吧？json不好用？？

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json是啥东东？怎么用？
我是想把name:value这些字段都解析出来，不管用什么方法
马上给分！！！

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一维数组的时候直接这么搞就行，二维的就不会了
eval("data = " + polylines);

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假设 str 中存储的为上述代码

JScript code:

eval("var obj = {" + 'polylines: [{ id: "transit_leg_0_0",