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  • JavaScript 判断变量是否为空---三元运算,元组获取值-重组.map()。

    var from_days = getQueryString('from_days');
    undefined
    {'from_days': (from_days) ? from_days : null}
    {from_days: null}
    var from_hours = getQueryString('from_hours')
    undefined
    {'from_days': (from_hours) ? from_hours : null}
    {from_days: "1"}
    cpu_data =  [['11:02:42', 12.3], ['11:02:47', 11.4], ['11:02:52', 13.3], ['11:02:57', 9.5], ['11:03:02', 12.6], ['11:03:07', 9.2]]
    (6) [Array(2), Array(2), Array(2), Array(2), Array(2), Array(2)]
    time_list = cpu_data.map(item =>item[0])
    (6) ["11:02:42", "11:02:47", "11:02:52", "11:02:57", "11:03:02", "11:03:07"]

    .map() 应用https://www.jb51.net/article/150818.htm

     变量赋值时的三元运算写法

            var host = window.location.host;  //127.0.0.1
            var proto = window.location.protocol;
            var ws_proto = (proto === "http:" ? "ws:" : "wss:");
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  • 原文地址:https://www.cnblogs.com/zhangmingda/p/11578499.html
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