如何将字符串转成数组

怎么把key值里的字符串转成数组
var arr=[{"key":"庄,8,3,5"},{"key":"闲,7,7,7"},{"key":"庄,6,3,8"},{"key":"闲,1,2,4"},{"key":"庄,5,5,5"},{"key":"闲,9,9,9"}];

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javascriptvar arr=[{"key":"庄,8,3,5"},{"key":"闲,7,7,7"},{"key":"庄,6,3,8"},{"key":"闲,1,2,4"},{"key":"庄,5,5,5"},{"key":"闲,9,9,9"}];

for(i in arr) {
    var val = arr[i]['key'].split(',');
    console.log(val)
}