如何从typescript中的arraylist中获取最大日期
如何从typescript中的arraylist中获取最大日期
提问于 2017-07-22 16:36:46
我需要数组元素列表中的最大日期: start_time属性
{
"jobs" : [ {
"job_id" : 10,
"users" : [ {
"user_id" : 11,
"data_points" : [ {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "abc@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-21T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
} ]
} ]
} ]
}Stack Overflow用户
发布于 2017-07-22 22:11:54
您可以使用此函数计算日期数组的最大日期：
arr = ["2017-07-20T04:04:43.000Z", "2017-07-21T04:04:43.000Z","2017-07-20T04:04:43.000Z"];
new Date(Math.max.apply(null,
arr
.map(x => new Date(x))));特定的解决方案(仅适用于包含单元素数组的特定JSON )：
获取数据点列表
var data = {
"jobs" : [ {
"job_id" : 10,
"users" : [ {
"user_id" : 11,
"data_points" : [ {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "abc@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-21T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
} ]
} ]
} ]
};
var d = data["jobs"][0]["users"][0]["data_points"];
var max_start_time =
new Date(Math.max.apply(null,
d
.map(z =>
z["start_time"]
).map(w => new Date(w))));
console.log(max_start_time);
通用解决方案(您将获得一个由"job_id"和"user_id"索引的数组)。这等同于sql select job_id，user_id，max(start_time) from ...group by job_id，user_id
var data = {
"jobs" : [
{
"job_id" : 110,
"users" : [ {
"user_id" : 11,
"data_points" : [ {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "abc@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-21T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-07-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
} ]
} ]
},
{
"job_id" : 111,
"users" : [ {
"user_id" : 12,
"data_points" : [ {
"duration" : 0,
"start_time" : "2017-08-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "abc@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-08-21T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-08-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
} ]
},
{
"user_id" : 13,
"data_points" : [ {
"duration" : 0,
"start_time" : "2017-08-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "abc@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-08-21T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
}, {
"duration" : 0,
"start_time" : "2017-08-20T04:04:43.000Z",
"datastream" : "GENERIC",
"username" : "rs022015@gmail.com.com"
} ]
}]
}]
};
var max_start_time = {};
var r=data["jobs"].forEach(job =>
{
if (job.hasOwnProperty("job_id")) {
if (job.hasOwnProperty("users")) {
job["users"].forEach(userData =>
{
if (userData.hasOwnProperty("data_points")) {
max_start_time[[job["job_id"],userData["user_id"]]]=
new Date(Math.max.apply(null,
userData["data_points"]
.map(z =>
z["start_time"]
).map(w => new Date(w))));
}
}
)
}
}
}
);
console.log(max_start_time);
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原文链接：
https://stackoverflow.com/questions/45252465
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