问使用JavaScript如何取Json格式下数组中数组的值？

[
    {
        "index":0,
        "fileList":[
            {
                "num":0,
                "fileUrl":"projectChange/0/20210103/1fcd55eeb7e141da80fde2db00439ee9.txt",
                "fileDesc":"Maven管理.txt"
            }
        ],
        "changeDesc":"48646",
        "changeTypeId":"70"
    },
    {
        "index":1,
        "fileList":[
            {
                "num":0,
                "fileUrl":"projectChange/81/20210103/5606619880684cc4a9450b4a97fd6159.docx",
                "fileDesc":"Navicat.docx"
            }
        ],
        "changeDesc":"45846",
        "changeTypeId":"69"
    }
]