更新时间:2023-01-30 09:12:03
这看起来像a map $ c>
reduce
问题,高级解决方案如下:
这是一个逐步的方法来实现这一点:
现在按月 - / p>
示例:
var l = [...]
var o = {};
var f = function(x){
var dt_object = Date(x [LAST_SUCCESSFUL_CONNECT]); // convert to datetime object
var key = dt_object.year +' - '+ dt_object.month;
if(o [key] === undefined){
var o [key] = [];
};
o [key] .push(x)
}
_.map(l,f(x))//将f应用于l $的每个成员b $ b
例如:
var g = function(member_count){
// extra logic may go here
return member_count
}
在o中的成员$ {
count = _.reduce(l,g(member))
member ['count'] = count
}
o ['month-year'] //用于该月份的字典列表
o ['month-year'] ['count'] //用于该月份中字典列表的计数。
对于JavaScript中的映射
和函数,请参阅underscore.js:
http://underscorejs.org/#map
http://underscorejs.org/#reduce
JavaScript日期对象:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
有关Date和DateTime对象的更多信息:
https://en.wikipedia.org/wiki/ISO_8601
有关 map的更多信息
reduce
:I'm using JavaScript. I have a JSON array that contains data in this format:
[
{"USER_NAME":"User1","LAST_SUCCESSFUL_CONNECT":"1373978337642"},
{"USER_NAME":"User2","LAST_SUCCESSFUL_CONNECT":"1374515704026"},
{"USER_NAME":"User3","LAST_SUCCESSFUL_CONNECT":"1374749782479"}
]
(the numbers above represent UTC date/time in milliseconds.
I would like to group (count) the data by month. Something like this:
[
{"Month":"January, 2014","User_Count": 2},
{"Month":"February, 2014","User_Count": 1},
]
I could use jQuery if it simplifies matters.
This looks like a map
reduce
problem. The high-level solution is as follows:
Here is a step-by-step how-to for achieving this:
These are now grouped by month-year.
Example:
var l = [...];
var o = {};
var f = function(x){
var dt_object = Date(x["LAST_SUCCESSFUL_CONNECT"]); // convert to datetime object
var key = dt_object.year + '-' + dt_object.month;
if (o[key] === undefined) {
var o[key] = [];
};
o[key].push(x)
}
_.map(l, f(x)) //apply f to each member of l
count
as key and length of list as its value.Example:
var g = function(member_count){
//extra logic may go here
return member_count
}
for member in o {
count = _.reduce(l, g(member))
member['count'] = count
}
o['month-year'] //for list of dictionaries in that month
o['month-year']['count'] //for the count of list of dictionaries in that month.
For map
and reduce
functions in javascript see underscore.js:
http://underscorejs.org/#map
http://underscorejs.org/#reduce
Javascript Date object:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
For more information on Date and DateTime objects:
https://en.wikipedia.org/wiki/ISO_8601
For more information on map
reduce
:
https://en.wikipedia.org/wiki/MapReduce