怎么把一个二维数组格式的字符串转换成js对象

如何把一个二维数组格式的字符串转换成js对象
var str="[
['A','B','C','D','E','F','G'],
['1','5.1','2','1.4','1.4','1'],
['2','5.4','1.8','1.6','1.7','2'],
['3','5.2','1.7','1.5','1.6','3']
 ]"

这个字符串如何转成js二维数组对象?
------解决思路----------------------
var str="[\
['A','B','C','D','E','F','G'],\
['1','5.1','2','1.4','1.4','1'],\
['2','5.4','1.8','1.6','1.7','2'],\
['3','5.2','1.7','1.5','1.6','3']\
 ]";
o = eval('('+str+')')
document.write(o[2][3]);
1.6
------解决思路----------------------
eval(str)