Functional JavaScript scratchpad

data.json

// Test data only, sourced from a JSON/YAML style data set; this
// is not realistic in production as the data would be normalised
// and the repetitive nature would be avoided, but it's a reality
// when you're setting up test data by hand, so valid. This data
// is referred to later as "d.employees"

[
   {
      "name":"Employee Zero",
      "wbses":[
         {
            "id":"wbs-1",
            "description":"this is the WBS 1"
         }
      ]
   },
   {
      "name":"Employee One",
      "wbses":[
         {
            "id":"wbs-1",
            "description":"this is the WBS 1"
         },
         {
            "id":"wbs-2",
            "description":"this is the WBS 2"
         },
         {
            "id":"wbs-3",
            "description":"this is the WBS 3"
         }
      ]
   },
   {
      "name":"Employee Two",
      "wbses":[
         {
            "id":"wbs-2",
            "description":"this is the WBS 2"
         },
         {
            "id":"wbs-3",
            "description":"this is the WBS 3"
         }
      ]
   },
   {
      "name":"Employee Three",
      "wbses":[
         {
            "id":"wbs-3",
            "description":"this is the WBS 3"
         }
      ]
   }
]

getProp.js

// property getter to be used in a map() call
getProp = function(p) {
    return function(m) {
        return m[p];
    };
};

nubBy.js

// This function written with Joseph (@jcla1) after discussion in the UI5 model 
// binding context. It's much better as it gives directly what is needed; it uses
// an index and an array, keeping track of uniqueness with the index. Lovely!
nubBy = function(key) {
   return function(map, item) {
      // set up map if required
      ["index", "array"].forEach(function(key) {
         if (!map.hasOwnProperty(key)) { map[key] = []; }
      });
      var id = item[key];
      if (map.index.indexOf(id) === -1) {
         map.index.push(id);
         map.array.push(item);
      }
      return map;
  };
}

reduceToArray.js

// returns reducer function to return a unique list
// of values for a given property
reduceToArray = function(key) {
    return function(array, item) {
        if (array.indexOf(item[key]) === -1) {
            array.push(item[key]);
        }
        return array;
    }
}

reduceToMap.js

// returns reducer function to return a map of maps
// that is unique based on the value of a given property
reduceToMap = function(key) {
    return function(map, item) {
        if (Object.keys(map).indexOf(item[key]) === -1) {
            map[item[key]] = item;
        }
        return map;
    };
}

usage-1.json

// Get unflat list of all WBSes
// d.employees.map(getProp('wbses'))
// =>

[
   [
      {
         "id":"wbs-1",
         "description":"this is the WBS 1"
      }
   ],
   [
      {
         "id":"wbs-1",
         "description":"this is the WBS 1"
      },
      {
         "id":"wbs-2",
         "description":"this is the WBS 2"
      },
      {
         "id":"wbs-3",
         "description":"this is the WBS 3"
      }
   ],
   [
      {
         "id":"wbs-2",
         "description":"this is the WBS 2"
      },
      {
         "id":"wbs-3",
         "description":"this is the WBS 3"
      }
   ],
   [
      {
         "id":"wbs-3",
         "description":"this is the WBS 3"
      }
   ]
]

usage-2.json

// Get unflat list of all WBSes
// Flatten it with concat
// Array.prototype.concat.apply([], d.employees.map(getProp('wbses')))
// =>

[
   {
      "id":"wbs-1",
      "description":"this is the WBS 1"
   },
   {
      "id":"wbs-1",
      "description":"this is the WBS 1"
   },
   {
      "id":"wbs-2",
      "description":"this is the WBS 2"
   },
   {
      "id":"wbs-3",
      "description":"this is the WBS 3"
   },
   {
      "id":"wbs-2",
      "description":"this is the WBS 2"
   },
   {
      "id":"wbs-3",
      "description":"this is the WBS 3"
   },
   {
      "id":"wbs-3",
      "description":"this is the WBS 3"
   }
]

usage-3.json

// Get unflat list of all WBSes
// Flatten it with concat
// Reduce to a list of unique WBSes
// Array.prototype.concat.apply([], d.employees.map(getProp('wbses'))).reduce(reduceToArray('id'), [])
// =>

[
   "wbs-1",
   "wbs-2",
   "wbs-3"
]

usage-4.json

// Get unflat list of all WBSes
// Flatten it with concat
// Reduce to a map of full-detail unique WBSes
// Array.prototype.concat.apply([], d.employees.map(getProp('wbses'))).reduce(reduceToMap('id'), {})
// =>

{
   "wbs-1":{
      "id":"wbs-1",
      "description":"this is the WBS 1"
   },
   "wbs-2":{
      "id":"wbs-2",
      "description":"this is the WBS 2"
   },
   "wbs-3":{
      "id":"wbs-3",
      "description":"this is the WBS 3"
   }
}

usage-5.json

// Get unflat list of all WBSes
// Flatten it with concat
// Reduce to an index of unique ids with an array of full-detail unique WBSes
// The data in "array" is ready for setting in a client model in UI5, for example
// Array.prototype.concat.apply([], d.employees.map(getProp('wbses'))).reduce(nubBy('id'), {})
// =>

{
   "index":[
      "wbs-1",
      "wbs-2",
      "wbs-3"
   ],
   "array":[
      {
         "id":"wbs-1",
         "description":"this is the WBS 1"
      },
      {
         "id":"wbs-2",
         "description":"this is the WBS 2"
      },
      {
         "id":"wbs-3",
         "description":"this is the WBS 3"
      }
   ]
}