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https://github.com/shimondoodkin/groupbyfunctions

global, easy to use, group by functions on objects. like linq - but much more simple and functional javascript
https://github.com/shimondoodkin/groupbyfunctions

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global, easy to use, group by functions on objects. like linq - but much more simple and functional javascript

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# groupbyfunctions

global, easy to use, group by functions on objects. like linq - but much more simple and functional javascript



Here are few function I used to copy paste to do simple jobs.



So I decided to make them global and make a module from them. 



```text



tests:



  groupby

    ✓ should sort items into buckets. return an object - put each item of an array into an object property, according to value of a specified field



  objeach

    ✓ should be iterate for each on object's properties



  objmap

    ✓ should be return a new object with same names and values updated by map function



  objfilter

    ✓ should be return a new object with properties filtered by their value



  sortobj

    ✓ should sort object's keys by their names

    ✓ should be able to use optional comparator



  sortobjkey

    ✓ should sort object's keys by value is desc order



  sortkeys

    ✓ should sort object's keys by their names

    ✓ should be able to use optional comparator



  objtokvarr

    ✓ should convert object to array of objects of key and value

    ✓ should be able to use defined names



  objtsv

    ✓ should convert array of objects to tab seperated values string



  12 passing (33ms)

```



``` npm install groupbyfunctions ```



examples use:



```javascript



var items=[

{id:1,kind:'type-b',value:997454},

{id:2,kind:'type-a',value:12132},

{id:3,kind:'type-a',value:451},

{id:4,kind:'type-c',value:7894}];



require('groupbyfunctions')



groupby(items,'kind') 

//result:

{ 'type-b': [ { id: 1, kind: 'type-b', value: 997454 } ],

  'type-a':

   [ { id: 2, kind: 'type-a', value: 12132 },

     { id: 3, kind: 'type-a', value: 451 } ],

  'type-c': [ { id: 4, kind: 'type-c', value: 7894 } ] }



sortobj(groupby(items,'kind'),function(av,bv,ak,bk){return bv.length-av.length})

//result:

{ 'type-a':

   [ { id: 2, kind: 'type-a', value: 12132 },

     { id: 3, kind: 'type-a', value: 451 } ],

  'type-b': [ { id: 1, kind: 'type-b', value: 997454 } ],

  'type-c': [ { id: 4, kind: 'type-c', value: 7894 } ] }



objmap(   groupby(items,'kind')  ,  function(items){ return items.length}  )

//result:

{ 'type-b': 1, 'type-a': 2, 'type-c': 1 }



objfilter(groupby(items,'kind'),function(v,k,i){ return v.length>1})

//result:

{ 'type-a':

   [ { id: 2, kind: 'type-a', value: 12132 },

     { id: 3, kind: 'type-a', value: 451 } ] }



     

var menu=objtokvarr(groupby(items,'kind'),'name','children')

// result:

[ { name: 'type-b',

    children: [ { id: 1, kind: 'type-b', value: 997454 } ] },

  { name: 'type-a',

    children:

     [ { id: 2, kind: 'type-a', value: 12132 },

       { id: 3, kind: 'type-a', value: 451 } ] },

  { name: 'type-c',

    children: [ { id: 4, kind: 'type-c', value: 7894 } ] } ]



//write single level object to string file (tab-seperated-values)

fs.writeFileSync('items.tsv',objtsv(items));



```



the functions:



```javascript



// receives an array

// returns an object,

//  the keys of it are as value of specified field,

//  the values of it are arrays of elements.

groupby=function (objarr,field)

{

    var existingGroups=[];

    var grouped={};

    objarr.forEach(function(obj)

    {

        var groupname=obj[field];

        if(groupname in grouped)

         grouped[groupname].push(obj);

        else

         grouped[groupname]=[obj];

    });

    return grouped;

}



// for each on object keys

//objeach(obj, function(value,key,index){ } )

objeach=function (obj,func)

{

    return Object.keys(obj).forEach(function(k,i)

    {

        return func(obj[k],k,i);

    });

}



//var obj=objmap(obj, function(value,key,index){ return value.field ; } )

objmap=function (obj,func)

{

 var r={};

 objeach(obj,function(v,k,i){r[k]=func(v,k,i)})

 return r;

}



//var obj=objmap(obj, function(value,key,index){ return value.field ; } )

objfilter=function (obj,func)

{

 var r={};

 objeach(obj,function(v,k,i){ if(func(v,k,i)) r[k]=v})

 return r;

}



// sort object keys by theis values

// sortobj(obj);

//

// sortobj(obj,function compfunc(a,b,aname,bname){ return b.field - a.field; });

//

//  comparator function is optional:

//   a comparator function returns 0 if parameters eqals,

//   a larger than zero value if a larger than b, or 

//   a less than zero value if a is smaler than b

//

//  in my comparator there are also aname and bname arguments it is possible to use them optionally.

//

//  exampels for comparator functions

//

//  //objct's sub property

//  sortobj(obj,function compfunc(a,b,aname,bname) 

//  {

//    if(a.field>b.field) return 1;

//    if(a.fieldb.field) return 1;   // first sort by this fileld

//    if(a.fieldb.fieldb) return 1; // if fields above is eqals, then sort by this fileld

//    if(a.fieldbbname) return 1;if(anameb[1]) return 1;if(a[1]b[1][k]) return -1;if(a[1][k] (http://doodkin.com)



But you can use it as you like, I don't care , Enjoy.