问题
Grouping elements in array by multiple properties is the closest match to my question as it indeed groups objects by multiple keys in an array. Problem is this solution doesn't sum up the properties value then remove the duplicates, it instead nests all the duplicates in a two-dimensional arrays.
Expected behavior
I have an array of objects which must be grouped by shape and color.
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 5},
{shape: 'square', color: 'red', used: 2, instances: 1}
];
Objects in this array are considered duplicates only if both their shape and color are the same. If they are, I want to respectively sum up their used and instances values then delete the duplicates.
So in this example result array may only contain four combinations : square red, square blue, circle red, circle blue
Problem
I tried a simpler approach here:
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'red', used: 4, instances: 4},
{shape: 'square', color: 'red', used: 2, instances: 2}
];
result = [];
arr.forEach(function (a) {
if ( !this[a.color] && !this[a.shape] ) {
this[a.color] = { color: a.color, shape: a.shape, used: 0, instances: 0 };
result.push(this[a.color]);
}
this[a.color].used += a.used;
this[a.color].instances += a.instances;
}, Object.create(null));
console.log(result);but it outputs
[{shape: "square", color: "red", used: 11, instances: 9},
{shape: "circle", color: "blue", used: 4, instances: 4}]
instead of expected result:
[{shape: "square", color: "red", used: 5, instances: 3},
{shape: "circle", color: "red", used: 2, instances: 1},
{shape: "square", color: "blue", used: 11, instances: 9},
{shape: "circle", color: "blue", used: 0, instances: 0}]
How can I get my function to properly group the objects by shape and color ? i.e. sum up their values and remove the duplicates ?
回答1:
Use Array#reduce with a helper object to group similar objects. For each object, check if the combined shape and color exists in the helper. If it doesn't, add to the helper using Object#assign to create a copy of the object, and push to the array. If it does, add it's values to used and instances.
var arr = [{"shape":"square","color":"red","used":1,"instances":1},{"shape":"square","color":"red","used":2,"instances":1},{"shape":"circle","color":"blue","used":0,"instances":0},{"shape":"square","color":"blue","used":4,"instances":4},{"shape":"circle","color":"red","used":1,"instances":1},{"shape":"circle","color":"red","used":1,"instances":0},{"shape":"square","color":"blue","used":4,"instances":5},{"shape":"square","color":"red","used":2,"instances":1}];
var helper = {};
var result = arr.reduce(function(r, o) {
var key = o.shape + '-' + o.color;
if(!helper[key]) {
helper[key] = Object.assign({}, o); // create a copy of o
r.push(helper[key]);
} else {
helper[key].used += o.used;
helper[key].instances += o.instances;
}
return r;
}, []);
console.log(result);If you can use ES6, you use a Map to collect the values, and then convert it back to an array by spreading the Map#values:
const arr = [{"shape":"square","color":"red","used":1,"instances":1},{"shape":"square","color":"red","used":2,"instances":1},{"shape":"circle","color":"blue","used":0,"instances":0},{"shape":"square","color":"blue","used":4,"instances":4},{"shape":"circle","color":"red","used":1,"instances":1},{"shape":"circle","color":"red","used":1,"instances":0},{"shape":"square","color":"blue","used":4,"instances":5},{"shape":"square","color":"red","used":2,"instances":1}];
const result = [...arr.reduce((r, o) => {
const key = o.shape + '-' + o.color;
const item = r.get(key) || Object.assign({}, o, {
used: 0,
instances: 0
});
item.used += o.used;
item.instances += o.instances;
return r.set(key, item);
}, new Map).values()];
console.log(result);回答2:
You can use reduce() to create one object of unique shape|color properties and Object.values() to return array of those values.
var arr =[{"shape":"square","color":"red","used":1,"instances":1},{"shape":"square","color":"red","used":2,"instances":1},{"shape":"circle","color":"blue","used":0,"instances":0},{"shape":"square","color":"blue","used":4,"instances":4},{"shape":"circle","color":"red","used":1,"instances":1},{"shape":"circle","color":"red","used":1,"instances":0},{"shape":"square","color":"blue","used":4,"instances":5},{"shape":"square","color":"red","used":2,"instances":1}]
var result = Object.values(arr.reduce(function(r, e) {
var key = e.shape + '|' + e.color;
if (!r[key]) r[key] = e;
else {
r[key].used += e.used;
r[key].instances += e.instances
}
return r;
}, {}))
console.log(result)回答3:
You could use a hash table and the keys for grouping same groups.
var array = [{ shape: 'square', color: 'red', used: 1, instances: 1 }, { shape: 'square', color: 'red', used: 2, instances: 1 }, { shape: 'circle', color: 'blue', used: 0, instances: 0 }, { shape: 'square', color: 'blue', used: 4, instances: 4 }, { shape: 'circle', color: 'red', used: 1, instances: 1 }, { shape: 'circle', color: 'red', used: 1, instances: 0 }, { shape: 'square', color: 'blue', used: 4, instances: 5 }, { shape: 'square', color: 'red', used: 2, instances: 1 }],
hash = Object.create(null),
grouped = [];
array.forEach(function (o) {
var key = ['shape', 'color'].map(function (k) { return o[k]; }).join('|');
if (!hash[key]) {
hash[key] = { shape: o.shape, color: o.color, used: 0, instances: 0 };
grouped.push(hash[key]);
}
['used', 'instances'].forEach(function (k) { hash[key][k] += o[k]; });
});
console.log(grouped);.as-console-wrapper { max-height: 100% !important; top: 0; }回答4:
Use this method to specify multiple properties:
public static groupBy(array, f) {
let groups = {};
array.forEach(function (o) {
var group = JSON.stringify(f(o));
groups[group] = groups[group] || [];
groups[group].push(o);
});
return Object.keys(groups).map(function (group) {
return groups[group];
})
}
Call this method like:
var result = Utils.groupBy(arr, function (item) {
return [item.shape, item.color];
});
回答5:
I have a suggestion for you. If you want to make it easier to do, you try the Underscore library : http://underscorejs.org/
I tried quickly to use it and got the right result :
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 5},
{shape: 'square', color: 'red', used: 2, instances: 1}
];
var byshape = _.groupBy(arr, 'shape');
var bycolor = _.map(byshape, function(array) {
return _.groupBy(array, 'color')
});
var output = [];
_.each(bycolor, function(arrayOfShape) {
_.each(arrayOfShape, function(arrayOfColor) {
var computedItem = {shape: "", color: "", used: 0, instances: 0};
_.each(arrayOfColor, function(item) {
computedItem.shape = item.shape;
computedItem.color = item.color;
computedItem.used += item.used;
computedItem.instances += item.instances;
});
output.push(computedItem);
});
});
console.log(output);
http://jsfiddle.net/oLyzdoo7/
This solution groups first data, then you can do what you want after, for example, compute data as ypur wish.
Maybe you can optimize it, let me know if you need more help
回答6:
/**
* Groups an array of objects with multiple properties.
*
* @param {Array} array: the array of objects to group
* @param {Array} props: the properties to groupby
* @return {Array} an array of arrays with the grouped results
*/
const groupBy = ({ Group: array, By: props }) => {
getGroupedItems = (item) => {
returnArray = [];
let i;
for (i = 0; i < props.length; i++) {
returnArray.push(item[props[i]]);
}
return returnArray;
};
let groups = {};
let i;
for (i = 0; i < array.length; i++) {
const arrayRecord = array[i];
const group = JSON.stringify(getGroupedItems(arrayRecord));
groups[group] = groups[group] || [];
groups[group].push(arrayRecord);
}
return Object.keys(groups).map((group) => {
return groups[group];
});
};
Example:
Assume that we have an array of objects. Each object contains info about a person and the money that possess. We want to sum up the money for all persons with the same Nationality and with the same gender.
const data = [
{Name: 'George', Surname: 'Best', Country: 'Great Britain', Gender: 'Male', Money:8000},
{Name: 'Orion', Surname: 'Papathanasiou', Country: 'Greece', Gender: 'Male', Money: 2000},
{Name: 'Mairy', Surname: 'Wellbeck', Country: 'Great Britain', Gender: 'Female', Money:5000},
{Name: 'Thanasis', Surname: 'Papathanasiou', Country: 'Greece',Gender: 'Male', Money: 3200},
{Name: 'George', Surname: 'Washington', Country: 'Great Britain', Gender: 'Male',Money:4200},
{Name: 'Orfeas', Surname: 'Kalaitzis', Country: 'Greece', Gender: 'Male', Money: 7643},
{Name: 'Nick', Surname: 'Wellington', Country: 'USA', Gender: 'Male', Money:1000},
{Name: 'Kostas', Surname: 'Antoniou', Country: 'Greece', Gender: 'Male', Money: 8712},
{Name: 'John', Surname: 'Oneal', Country: 'USA', Gender: 'Male', Money:98234},
{Name: 'Paulos', Surname: 'Stamou', Country: 'Greece', Gender: 'Male', Money: 3422},
{Name: 'Soula', Surname: 'Spuropoulou', Country: 'Greece', Gender: 'Female', Money:400},
{Name: 'Paul', Surname: 'Pierce', Country: 'USA', Gender: 'Male',Money: 13000},
{Name: 'Helen', Surname: 'Smith', Country: 'Great Britain', Gender: 'Female', Money:1000},
{Name: 'Cathrine', Surname: 'Bryant', Country: 'Great Britain', Gender: 'Female', Money: 8712},
{Name: 'Jenny', Surname: 'Scalabrini', Country: 'USA', Gender: 'Female', Money:92214}];
const groupByProperties = ['Country', 'Gender'];
Calling the function:
const groupResult = groupBy( {Group: data, By: groupByProperties} );
The group result is:
(6) [Array(2), Array(5), Array(3), Array(3), Array(1), Array(1)]
0: Array(2)
0: {Name: "George", Surname: "Best", Country: "Great Britain", Gender: "Male", Money: 8000}
1: {Name: "George", Surname: "Washington", Country: "Great Britain", Gender: "Male", Money: 4200}
length: 2
__proto__: Array(0)
1: Array(5)
0: {Name: "Orion", Surname: "Papathanasiou", Country: "Greece", Gender: "Male", Money: 2000}
1: {Name: "Thanasis", Surname: "Papathanasiou", Country: "Greece", Gender: "Male", Money: 3200}
2: {Name: "Orfeas", Surname: "Kalaitzis", Country: "Greece", Gender: "Male", Money: 7643}
3: {Name: "Kostas", Surname: "Antoniou", Country: "Greece", Gender: "Male", Money: 8712}
4: {Name: "Paulos", Surname: "Stamou", Country: "Greece", Gender: "Male", Money: 3422}
length: 5
__proto__: Array(0)
2: Array(3)
0: {Name: "Mairy", Surname: "Wellbeck", Country: "Great Britain", Gender: "Female", Money: 5000}
1: {Name: "Helen", Surname: "Smith", Country: "Great Britain", Gender: "Female", Money: 1000}
2: {Name: "Cathrine", Surname: "Bryant", Country: "Great Britain", Gender: "Female", Money: 8712}
length: 3
__proto__: Array(0)
3: Array(3)
0: {Name: "Nick", Surname: "Wellington", Country: "USA", Gender: "Male", Money: 1000}
1: {Name: "John", Surname: "Oneal", Country: "USA", Gender: "Male", Money: 98234}
2: {Name: "Paul", Surname: "Pierce", Country: "USA", Gender: "Male", Money: 13000}
length: 3
__proto__: Array(0)
4: Array(1)
0: {Name: "Soula", Surname: "Spuropoulou", Country: "Greece", Gender: "Female", Money: 400}
length: 1
__proto__: Array(0)
5: Array(1)
0: {Name: "Jenny", Surname: "Scalabrini", Country: "USA", Gender: "Female", Money: 92214}
length: 1
__proto__: Array(0)
length: 6
__proto__: Array(0)
So, we got 6 arrays. Each array is grouped by Country and by Gender
Iterating over each array, we can sum up the money!
const groupBy = ({ Group: array, By: props }) => {
getGroupedItems = (item) => {
returnArray = [];
let i;
for (i = 0; i < props.length; i++) {
returnArray.push(item[props[i]]);
}
return returnArray;
};
let groups = {};
let i;
for (i = 0; i < array.length; i++) {
const arrayRecord = array[i];
const group = JSON.stringify(getGroupedItems(arrayRecord));
groups[group] = groups[group] || [];
groups[group].push(arrayRecord);
}
return Object.keys(groups).map((group) => {
return groups[group];
});
};
const data = [
{Name: 'George', Surname: 'Best', Country: 'Great Britain', Gender: 'Male', Money:8000},
{Name: 'Orion', Surname: 'Papathanasiou', Country: 'Greece', Gender: 'Male', Money: 2000},
{Name: 'Mairy', Surname: 'Wellbeck', Country: 'Great Britain', Gender: 'Female', Money:5000},
{Name: 'Thanasis', Surname: 'Papathanasiou', Country: 'Greece',Gender: 'Male', Money: 3200},
{Name: 'George', Surname: 'Washington', Country: 'Great Britain', Gender: 'Male',Money:4200},
{Name: 'Orfeas', Surname: 'Kalaitzis', Country: 'Greece', Gender: 'Male', Money: 7643},
{Name: 'Nick', Surname: 'Wellington', Country: 'USA', Gender: 'Male', Money:1000},
{Name: 'Kostas', Surname: 'Antoniou', Country: 'Greece', Gender: 'Male', Money: 8712},
{Name: 'John', Surname: 'Oneal', Country: 'USA', Gender: 'Male', Money:98234},
{Name: 'Paulos', Surname: 'Stamou', Country: 'Greece', Gender: 'Male', Money: 3422},
{Name: 'Soula', Surname: 'Spuropoulou', Country: 'Greece', Gender: 'Female', Money:400},
{Name: 'Paul', Surname: 'Pierce', Country: 'USA', Gender: 'Male',Money: 13000},
{Name: 'Helen', Surname: 'Smith', Country: 'Great Britain', Gender: 'Female', Money:1000},
{Name: 'Cathrine', Surname: 'Bryant', Country: 'Great Britain', Gender: 'Female', Money: 8712},
{Name: 'Jenny', Surname: 'Scalabrini', Country: 'USA', Gender: 'Female', Money:92214}];
const groupByProperties = ['Country', 'Gender'];
const groupResult = groupBy( {Group: data, By: groupByProperties} );
console.log(groupResult);回答7:
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 5},
{shape: 'square', color: 'red', used: 2, instances: 1}
];
result = [];
arr.forEach(function (a) {
if ( !this[a.color] && !this[a.shape] ) {
this[a.color] = { color: a.color, shape: a.shape, used: 0, instances: 0 };
result.push(this[a.color]);
}
this[a.color].used += a.used;
this[a.color].instances += a.instances;
}, Object.create(null));
console.log(result);
**Output:**
[
{
"color": "red",
"shape": "square",
"used": 11,
"instances": 9
},
{
"color": "blue",
"shape": "circle",
"used": 4,
"instances": 4
}
]
thats all perfetcly working.
Enjoy your coding....
回答8:
ES6 answers as requisted by user:
// To call this function:
// const result = this.toolBox.multipleGroupByArray(
// dataArray, (property: IProperty) => [property.prop1, property.prop2, property.prop3]);
multipleGroupByArray(dataArray, groupPropertyArray) {
const groups = {};
dataArray.forEach(item => {
const group = JSON.stringify(groupPropertyArray(item));
groups[group] = groups[group] || [];
groups[group].push(item);
});
return Object.keys(groups).map(function(group) {
return groups[group];
});
}
回答9:
If you want groupBy keys as per conditional fields then here is the modification for @Abbes answer:
function groupBy(array, f) {
let groups = {};
array.forEach((o) => {
var group = f(o).join('-');
groups[group] = groups[group] || [];
groups[group].push(o);
});
return groups;
}
And use it like:
groupBy(connectedServers, (item) => {
return [item.key1, item.key2];
});
来源：https://stackoverflow.com/questions/46794232/group-objects-by-multiple-properties-in-array-then-sum-up-their-values