I'd like to sum the values of an object.
I'm used to python where it would just be:
sample = { 'a': 1 , 'b': 2 , 'c':3 };
summed = sum(sample.itervalues())
The following code works, but it's a lot of code:
function obj_values(object) {
var results = [];
for (var property in object)
results.push(object[property]);
return results;
}
function list_sum( list ){
return list.reduce(function(previousValue, currentValue, index, array){
return previousValue + currentValue;
});
}
function object_values_sum( obj ){
return list_sum(obj_values(obj));
}
var sample = { a: 1 , b: 2 , c:3 };
var summed = list_sum(obj_values(a));
var summed = object_values_sum(a)
Am i missing anything obvious, or is this just the way it is?
It can be as simple as that:
const sumValues = obj => Object.values(obj).reduce((a, b) => a + b, 0);
Quoting MDN:
The Object.values() method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).
from Object.values() on MDN
The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.
from Array.prototype.reduce() on MDN
You can use this function like that:
sumValues({a: 4, b: 6, c: -5, d: 0}); // gives 5
Note that this code uses some ECMAScript features which are not supported by some older browsers (like IE). You might need to use Babel to compile your code.
You could put it all in one function:
function sum( obj ) {
var sum = 0;
for( var el in obj ) {
if( obj.hasOwnProperty( el ) ) {
sum += parseFloat( obj[el] );
}
}
return sum;
}
var sample = { a: 1 , b: 2 , c:3 };
var summed = sum( sample );
console.log( "sum: "+summed );
For fun's sake here is another implementation using Object.keys() and Array.reduce() (browser support should not be a big issue anymore):
function sum(obj) {
return Object.keys(obj).reduce((sum,key)=>sum+parseFloat(obj[key]||0),0);
}
let sample = { a: 1 , b: 2 , c:3 };
console.log(`sum:${sum(sample)}`);
But this seems to be way slower: jsperf.com
If you're using lodash you can do something like
_.sum(_.values({ 'a': 1 , 'b': 2 , 'c':3 }))
Now you can make use of reduce function and get the sum.
const object1 = { 'a': 1 , 'b': 2 , 'c':3 }
console.log(Object.values(object1).reduce((a, b) => a + b, 0));
A regular for loop is pretty concise:
var total = 0;
for (var property in object) {
total += object[property];
}
You might have to add in object.hasOwnProperty if you modified the prototype.
Honestly, given our "modern times" I'd go with a functional programming approach whenever possible, like so:
const sumValues = (obj) => Object.keys(obj).reduce((acc, value) => acc + obj[value], 0);
Our accumulator acc, starting with a value of 0, is accumulating all looped values of our object. This has the added benefit of not depending on any internal or external variables; it's a constant function so it won't be accidentally overwritten... win for ES2015!
Any reason you're not just using a simple for...in loop?
var sample = { a: 1 , b: 2 , c:3 };
var summed = 0;
for (var key in sample) {
summed += sample[key];
};
http://jsfiddle.net/vZhXs/
let prices = {
"apple": 100,
"banana": 300,
"orange": 250
};
let sum = 0;
for (let price of Object.values(prices)) {
sum += price;
}
alert(sum)
I am a bit tardy to the party, however, if you require a more robust and flexible solution then here is my contribution. If you want to sum only a specific property in a nested object/array combo, as well as perform other aggregate methods, then here is a little function I have been using on a React project:
var aggregateProperty = function(obj, property, aggregate, shallow, depth) {
//return aggregated value of a specific property within an object (or array of objects..)
if ((typeof obj !== 'object' && typeof obj !== 'array') || !property) {
return;
}
obj = JSON.parse(JSON.stringify(obj)); //an ugly way of copying the data object instead of pointing to its reference (so the original data remains unaffected)
const validAggregates = [ 'sum', 'min', 'max', 'count' ];
aggregate = (validAggregates.indexOf(aggregate.toLowerCase()) !== -1 ? aggregate.toLowerCase() : 'sum'); //default to sum
//default to false (if true, only searches (n) levels deep ignoring deeply nested data)
if (shallow === true) {
shallow = 2;
} else if (isNaN(shallow) || shallow < 2) {
shallow = false;
}
if (isNaN(depth)) {
depth = 1; //how far down the rabbit hole have we travelled?
}
var value = ((aggregate == 'min' || aggregate == 'max') ? null : 0);
for (var prop in obj) {
if (!obj.hasOwnProperty(prop)) {
continue;
}
var propValue = obj[prop];
var nested = (typeof propValue === 'object' || typeof propValue === 'array');
if (nested) {
//the property is an object or an array
if (prop == property && aggregate == 'count') {
value++;
}
if (shallow === false || depth < shallow) {
propValue = aggregateProperty(propValue, property, aggregate, shallow, depth+1); //recursively aggregate nested objects and arrays
} else {
continue; //skip this property
}
}
//aggregate the properties value based on the selected aggregation method
if ((prop == property || nested) && propValue) {
switch(aggregate) {
case 'sum':
if (!isNaN(propValue)) {
value += propValue;
}
break;
case 'min':
if ((propValue < value) || !value) {
value = propValue;
}
break;
case 'max':
if ((propValue > value) || !value) {
value = propValue;
}
break;
case 'count':
if (propValue) {
if (nested) {
value += propValue;
} else {
value++;
}
}
break;
}
}
}
return value;
}
It is recursive, non ES6, and it should work in most semi-modern browsers. You use it like this:
const onlineCount = aggregateProperty(this.props.contacts, 'online', 'count');
Parameter breakdown:
obj = either an object or an array
property = the property within the nested objects/arrays you wish to perform the aggregate method on
aggregate = the aggregate method (sum, min, max, or count)
shallow = can either be set to true/false or a numeric value
depth = should be left null or undefined (it is used to track the subsequent recursive callbacks)
Shallow can be used to enhance performance if you know that you will not need to search deeply nested data. For instance if you had the following array:
[
{
id: 1,
otherData: { ... },
valueToBeTotaled: ?
},
{
id: 2,
otherData: { ... },
valueToBeTotaled: ?
},
{
id: 3,
otherData: { ... },
valueToBeTotaled: ?
},
...
]
If you wanted to avoid looping through the otherData property since the value you are going to be aggregating is not nested that deeply, you could set shallow to true.
Use Lodash
import _ from 'Lodash';
var object_array = [{a: 1, b: 2, c: 3}, {a: 4, b: 5, c: 6}];
return _.sumBy(object_array, 'c')
// return => 9
I came across this solution from #jbabey while trying to solve a similar problem. With a little modification, I got it right. In my case, the object keys are numbers (489) and strings ("489"). Hence to solve this, each key is parse. The following code works:
var array = {"nR": 22, "nH": 7, "totB": "2761", "nSR": 16, "htRb": "91981"}
var parskey = 0;
for (var key in array) {
parskey = parseInt(array[key]);
sum += parskey;
};
return(sum);
A ramda one liner:
import {
compose,
sum,
values,
} from 'ramda'
export const sumValues = compose(sum, values);
Use:
const summed = sumValues({ 'a': 1 , 'b': 2 , 'c':3 });
We can iterate object using in keyword and can perform any arithmetic operation.
// input
const sample = {
'a': 1,
'b': 2,
'c': 3
};
// var
let sum = 0;
// object iteration
for (key in sample) {
//sum
sum += (+sample[key]);
}
// result
console.log("sum:=>", sum);
A simple solution would be to use the for..in loop to find the sum.
function findSum(obj){
let sum = 0;
for(property in obj){
sum += obj[property];
}
return sum;
}
var sample = { a: 1 , b: 2 , c:3 };
console.log(findSum(sample));
function myFunction(a) { return Object.values(a).reduce((sum, cur) => sum + cur, 0); }
Sum the object key value by parse Integer. Converting string format to integer and summing the values
var obj = {
pay: 22
};
obj.pay;
console.log(obj.pay);
var x = parseInt(obj.pay);
console.log(x + 20);
function totalAmountAdjectives(obj) {
let sum = 0;
for(let el in obj) {
sum += el.length;
}
return sum;
}
console.log(totalAmountAdjectives({ a: "apple" }))
A simple and clean solution for typescrip:
const sample = { a: 1, b: 2, c: 3 };
const totalSample = Object.values(sample).reduce(
(total: number, currentElement: number) => total + currentElement
);
console.log(totalSample);
Good luck!
Related
I try to write a function (called: tally) using recursion (part of the exercise) to scan through an array of numbers and return an object with the numbers as key and the number of instances as value.
Example:
tally([2,3,4,5,5,5,5,5,5,5,6,7,,6,7,6,7,5,4,3,4,5,5,6])
//{2: 1, 3: 2, 4: 3, 5: 10, 6: 4, 7: 3}
I created the framework but i am not sure about the syntax to make it work:
function tally(arr) {
var obj = {}
if (/*check if object ('obj') has a key corresponding to the array element*/) {
//increase key's value by onee
} else {
//add key with value of 1
}
return obj
};
Any hints to complete the recursion function above? Please try to stick to my structure in your answers as much as possible since this is part of an exercise.
Here you are:
function tally(arr) {
if (arr.length == 0) {
return {}
}
var value = arr.pop()
var obj = tally(arr)
if (value in obj) {
obj[value] += 1
} else {
obj[value] = 1
}
return obj
};
EDIT:
It can also be done using slice() instead of pop():
function tally(arr) {
if (arr.length == 0) {
return {}
}
var value = arr[0]
var obj = tally(arr.slice(1))
if (value in obj) {
obj[value] += 1
} else {
obj[value] = 1
}
return obj
};
Using extra parameter for an index, i, the result, r -
const plus1 = (k = "", r = {}) =>
( k in r
? r[k] += 1
: r[k] = 1
, r
)
const tally = (a = [], i = 0, r = {}) =>
i >= a.length
? r
: tally
( a
, i + 1
, plus1(a[i], r)
)
console.log(tally([2,3,4,5,5,5,5,5,5,5,6,7,,6,7,6,7,5,4,3,4,5,5,6]))
Output
{
"2": 1,
"3": 2,
"4": 3,
"5": 10,
"6": 4,
"7": 3,
"undefined": 1
}
ok, so you are asked to do a recursion just for the sake of it.
This could be done (albeit is hacky) passing an extra parameter to tally. When you declare a function in vanilla js you can actually feed it extra stuff. So, in each recursion, pass obj as a second parameter:
EDIT
Thanks #Bergi, you're right. I'll edit the code
function tally(arr) {
let obj = arguments.length>1? arguments[1] : {};
if(arr.length===0) {
return obj;
}
let next_number=arr.pop();
obj[next_number]=obj[next_number]||0;
obj[next_number]++;
return tally(arr,obj);
};
let inputArr = [2,3,4,5,5,5,5,5,5,5,6,7,6,7,6,7,5,4,3,4,5,5,6],
outputObj=tally(inputArr);
console.log(outputObj);
console.log({outputEmpty:tally([])});
I am not sure how to guide you to an answer without giving it away entirely, but this is what I would recommend. (There are some problems such as you destroy arr in the process that you may want to consider)
function tally(arr, obj) {
// if the length is zero we've gone through every value
if(arr.length === 0)
return obj
// create obj if we didn't provide it
if(obj === undefined)
obj = {}
// pull the last value from arr
let val = arr.pop()
if (/*check if object ('obj') has a key corresponding to the array element*/) {
//increase key's value by onee
} else {
//add key with value of 1
}
// move onto the next value
return tally(arr,obj)
}
EDIT: took #Bergi's input
Here is what I want to achieve:
A function called Splice which can take 3 arguments:
The first is an object.
The second is numeric.
The third is numeric.
It takes properties from an object and uses them for a newly created object.
Which properties are defined by the two numbers. The second argument indicates the position of the key/value pair that I want to start taking properties from and the third indicates how many I want to remove.
So for instance splice(0,2) refers to the positions 0 and 1 of the object having the following object: var obj = {a: 1, b: 2, c: 2} and calling the function splice with the arguments obj, 0, 2 should return {a: 1, b: 2}
If the third argument is not passed it should default to 1.
This is what I have so far (not yet respecting the last part when only one number is passed in):
function splice(object, number, number2) {
var newOjb = {};
var count = 0;
object.forEach(function(element, index) {
count++;
if(count <= number2 && count > number) {
newObj[key]=item
} else if (number == count) {
newObj[key]=item
}
})
return newObj;
}
However, I seem to use some wrong syntax as my console tells me my forEach loop is not a function and the code, in general, doesn't seem to work.
Any ideas for basic solutions (no fancy techniques)?
Use Object.entries(object).forEach(function([key, item], index) { (Note: This will not guarantee order). You have also typo in var newOjb = {};
P.S. You don't need that count, you can use index in your conditions
number - index, number2 - count
function splice(object, number, number2) {
var newObj = {};
if (!number2) {
number2 = 1;
}
Object.entries(object).forEach(function([key, item], index) {
if (index >= number && index - number < number2) {
newObj[key] = item
}
})
return newObj;
}
let obj = {
a: 1,
b: 2,
c: 2
};
console.log(splice(obj, 0, 2))
console.log(splice(obj, 2))
console.log(splice(obj, 1, 2))
FWIW, here's a function that behaves exactly like Array.splice for objects (don't know if this qualifies as "fancy" though):
function spliceObject(obj, start, deleteCount, ...items) {
let e = Object.entries(obj);
let r = e.splice(start, deleteCount, ...items.flatMap(Object.entries));
Object.keys(obj).forEach(k => delete obj[k]);
e.forEach(([k, v]) => obj[k] = v);
return Object.fromEntries(r);
}
//
obj = {a:1, b:2, c:3, d:4, e:5, f:6 }
ret = spliceObject(obj, 1, 3, {xyz:88}, {blah:99})
console.log(obj)
console.log(ret)
Do note however that you generally shouldn't rely on object properties being ordered in any particular way. The ordering is defined and mandated by the standard, but not all engines and tools get it right.
For your default value question, this is a pattern that works well
function myfunction1(val) {
this.val = val ? val : 1;
console.log(this.val);
}
My application has a large array of objects, which I stringify and save them to the disk. Unfortunately, when the objects in the array are manipulated, and sometimes replaced, the properties on the objects are listed in different orders (their creation order?). When I do JSON.stringify() on the array and save it, a diff shows the properties getting listed in different orders, which is annoying when trying to merge the data further with diff and merging tools.
Ideally I would like to sort the properties of the objects in alphabetical order prior to performing the stringify, or as part of the stringify operation. There is code for manipulating the array objects in many places, and altering these to always create properties in an explicit order would be difficult.
Suggestions would be most welcome!
A condensed example:
obj = {}; obj.name="X"; obj.os="linux";
JSON.stringify(obj);
obj = {}; obj.os="linux"; obj.name="X";
JSON.stringify(obj);
The output of these two stringify calls are different, and showing up in a diff of my data, but my application doesn't care about the ordering of properties. The objects are constructed in many ways and places.
The simpler, modern and currently browser supported approach is simply this:
JSON.stringify(sortMyObj, Object.keys(sortMyObj).sort());
However, this method does remove any nested objects that aren't referenced and does not apply to objects within arrays. You will want to flatten the sorting object as well if you want something like this output:
{"a":{"h":4,"z":3},"b":2,"c":1}
You can do that with this:
var flattenObject = function(ob) {
var toReturn = {};
for (var i in ob) {
if (!ob.hasOwnProperty(i)) continue;
if ((typeof ob[i]) == 'object') {
var flatObject = flattenObject(ob[i]);
for (var x in flatObject) {
if (!flatObject.hasOwnProperty(x)) continue;
toReturn[i + '.' + x] = flatObject[x];
}
} else {
toReturn[i] = ob[i];
}
}
return toReturn;
};
var myFlattenedObj = flattenObject(sortMyObj);
JSON.stringify(myFlattenedObj, Object.keys(myFlattenedObj).sort());
To do it programmatically with something you can tweak yourself, you need to push the object property names into an array, then sort the array alphabetically and iterate through that array (which will be in the right order) and select each value from the object in that order. "hasOwnProperty" is checked also so you definitely have only the object's own properties. Here's an example:
var obj = {"a":1,"b":2,"c":3};
function iterateObjectAlphabetically(obj, callback) {
var arr = [],
i;
for (i in obj) {
if (obj.hasOwnProperty(i)) {
arr.push(i);
}
}
arr.sort();
for (i = 0; i < arr.length; i++) {
var key = obj[arr[i]];
//console.log( obj[arr[i]] ); //here is the sorted value
//do what you want with the object property
if (callback) {
// callback returns arguments for value, key and original object
callback(obj[arr[i]], arr[i], obj);
}
}
}
iterateObjectAlphabetically(obj, function(val, key, obj) {
//do something here
});
Again, this should guarantee that you iterate through in alphabetical order.
Finally, taking it further for the simplest way, this library will recursively allow you to sort any JSON you pass into it: https://www.npmjs.com/package/json-stable-stringify
var stringify = require('json-stable-stringify');
var obj = { c: 8, b: [{z:6,y:5,x:4},7], a: 3 };
console.log(stringify(obj));
Output
{"a":3,"b":[{"x":4,"y":5,"z":6},7],"c":8}
I don't understand why the complexity of the current best answers is needed, to get all the keys recursively. Unless perfect performance is needed, it seems to me that we can just call JSON.stringify() twice, the first time to get all the keys, and the second time, to really do the job. That way, all the recursion complexity is handled by stringify, and we know that it knows its stuff, and how to handle each object type:
function JSONstringifyOrder(obj, space)
{
const allKeys = new Set();
JSON.stringify(obj, (key, value) => (allKeys.add(key), value));
return JSON.stringify(obj, Array.from(allKeys).sort(), space);
}
Or if you want to support older browsers:
function JSONstringifyOrder(obj, space)
{
var allKeys = [];
var seen = {};
JSON.stringify(obj, function (key, value) {
if (!(key in seen)) {
allKeys.push(key);
seen[key] = null;
}
return value;
});
allKeys.sort();
return JSON.stringify(obj, allKeys, space);
}
I think that if you are in control of the JSON generation (and it sounds like you are), then for your purposes this might be a good solution: json-stable-stringify
From the project website:
deterministic JSON.stringify() with custom sorting to get
deterministic hashes from stringified results
If the JSON produced is deterministic you should be able to easily diff/merge it.
You can pass a sorted array of the property names as the second argument of JSON.stringify():
JSON.stringify(obj, Object.keys(obj).sort())
JSON.stringify() replacer function for having object keys sorted in output (supports deeply nested objects).
const replacer = (key, value) =>
value instanceof Object && !(value instanceof Array) ?
Object.keys(value)
.sort()
.reduce((sorted, key) => {
sorted[key] = value[key];
return sorted
}, {}) :
value;
// Usage
// JSON.stringify({c: 1, a: { d: 0, c: 1, e: {a: 0, 1: 4}}}, replacer);
GitHub Gist page here.
Update 2018-7-24:
This version sorts nested objects and supports array as well:
function sortObjByKey(value) {
return (typeof value === 'object') ?
(Array.isArray(value) ?
value.map(sortObjByKey) :
Object.keys(value).sort().reduce(
(o, key) => {
const v = value[key];
o[key] = sortObjByKey(v);
return o;
}, {})
) :
value;
}
function orderedJsonStringify(obj) {
return JSON.stringify(sortObjByKey(obj));
}
Test case:
describe('orderedJsonStringify', () => {
it('make properties in order', () => {
const obj = {
name: 'foo',
arr: [
{ x: 1, y: 2 },
{ y: 4, x: 3 },
],
value: { y: 2, x: 1, },
};
expect(orderedJsonStringify(obj))
.to.equal('{"arr":[{"x":1,"y":2},{"x":3,"y":4}],"name":"foo","value":{"x":1,"y":2}}');
});
it('support array', () => {
const obj = [
{ x: 1, y: 2 },
{ y: 4, x: 3 },
];
expect(orderedJsonStringify(obj))
.to.equal('[{"x":1,"y":2},{"x":3,"y":4}]');
});
});
Deprecated answer:
A concise version in ES2016.
Credit to #codename , from https://stackoverflow.com/a/29622653/94148
function orderedJsonStringify(o) {
return JSON.stringify(Object.keys(o).sort().reduce((r, k) => (r[k] = o[k], r), {}));
}
This is same as Satpal Singh's answer
function stringifyJSON(obj){
keys = [];
if(obj){
for(var key in obj){
keys.push(key);
}
}
keys.sort();
var tObj = {};
var key;
for(var index in keys){
key = keys[index];
tObj[ key ] = obj[ key ];
}
return JSON.stringify(tObj);
}
obj1 = {}; obj1.os="linux"; obj1.name="X";
stringifyJSON(obj1); //returns "{"name":"X","os":"linux"}"
obj2 = {}; obj2.name="X"; obj2.os="linux";
stringifyJSON(obj2); //returns "{"name":"X","os":"linux"}"
A recursive and simplified answer:
function sortObject(obj) {
if(typeof obj !== 'object')
return obj
var temp = {};
var keys = [];
for(var key in obj)
keys.push(key);
keys.sort();
for(var index in keys)
temp[keys[index]] = sortObject(obj[keys[index]]);
return temp;
}
var str = JSON.stringify(sortObject(obj), undefined, 4);
You can sort object by property name in EcmaScript 2015
function sortObjectByPropertyName(obj) {
return Object.keys(obj).sort().reduce((c, d) => (c[d] = obj[d], c), {});
}
You can add a custom toJSON function to your object which you can use to customise the output. Inside the function, adding current properties to a new object in a specific order should preserve that order when stringified.
See here:
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/JSON/stringify
There's no in-built method for controlling ordering because JSON data is meant to be accessed by keys.
Here's a jsfiddle with a small example:
http://jsfiddle.net/Eq2Yw/
Try commenting out the toJSON function - the order of the properties is reversed. Please be aware that this may be browser-specific, i.e. ordering is not officially supported in the specification. It works in the current version of Firefox, but if you want a 100% robust solution, you may have to write your own stringifier function.
Edit:
Also see this SO question regarding stringify's non-deterministic output, especially Daff's details about browser differences:
How to deterministically verify that a JSON object hasn't been modified?
I took the answer from #Jason Parham and made some improvements
function sortObject(obj, arraySorter) {
if(typeof obj !== 'object')
return obj
if (Array.isArray(obj)) {
if (arraySorter) {
obj.sort(arraySorter);
}
for (var i = 0; i < obj.length; i++) {
obj[i] = sortObject(obj[i], arraySorter);
}
return obj;
}
var temp = {};
var keys = [];
for(var key in obj)
keys.push(key);
keys.sort();
for(var index in keys)
temp[keys[index]] = sortObject(obj[keys[index]], arraySorter);
return temp;
}
This fixes the issue of arrays being converted to objects, and it also allows you to define how to sort arrays.
Example:
var data = { content: [{id: 3}, {id: 1}, {id: 2}] };
sortObject(data, (i1, i2) => i1.id - i2.id)
output:
{content:[{id:1},{id:2},{id:3}]}
I just rewrote one of mentioned examples to use it in stringify
const stringifySort = (key, value) => {
if (!value || typeof value !== 'object' || Array.isArray(value)) return value;
return Object.keys(value).sort().reduce((obj, key) => (obj[key]=value[key], obj), {});
};
JSON.stringify({name:"X", os:"linux"}, stringifySort);
The accepted answer does not work for me for nested objects for some reason. This led me to code up my own. As it's late 2019 when I write this, there are a few more options available within the language.
Update: I believe David Furlong's answer is a preferable approach to my earlier attempt, and I have riffed off that. Mine relies on support for Object.entries(...), so no Internet Explorer support.
function normalize(sortingFunction) {
return function(key, value) {
if (typeof value === 'object' && !Array.isArray(value)) {
return Object
.entries(value)
.sort(sortingFunction || undefined)
.reduce((acc, entry) => {
acc[entry[0]] = entry[1];
return acc;
}, {});
}
return value;
}
}
JSON.stringify(obj, normalize(), 2);
--
KEEPING THIS OLDER VERSION FOR HISTORICAL REFERENCE
I found that a simple, flat array of all keys in the object will work. In almost all browsers (not Edge or Internet explorer, predictably) and Node 12+ there is a fairly short solution now that Array.prototype.flatMap(...) is available. (The lodash equivalent would work too.) I have only tested in Safari, Chrome, and Firefox, but I see no reason why it wouldn't work anywhere else that supports flatMap and standard JSON.stringify(...).
function flattenEntries([key, value]) {
return (typeof value !== 'object')
? [ [ key, value ] ]
: [ [ key, value ], ...Object.entries(value).flatMap(flattenEntries) ];
}
function sortedStringify(obj, sorter, indent = 2) {
const allEntries = Object.entries(obj).flatMap(flattenEntries);
const sorted = allEntries.sort(sorter || undefined).map(entry => entry[0]);
return JSON.stringify(obj, sorted, indent);
}
With this, you can stringify with no 3rd-party dependencies and even pass in your own sort algorithm that sorts on the key-value entry pairs, so you can sort by key, payload, or a combination of the two. Works for nested objects, arrays, and any mixture of plain old data types.
const obj = {
"c": {
"z": 4,
"x": 3,
"y": [
2048,
1999,
{
"x": false,
"g": "help",
"f": 5
}
]
},
"a": 2,
"b": 1
};
console.log(sortedStringify(obj, null, 2));
Prints:
{
"a": 2,
"b": 1,
"c": {
"x": 3,
"y": [
2048,
1999,
{
"f": 5,
"g": "help",
"x": false
}
],
"z": 4
}
}
If you must have compatibility with older JavaScript engines, you could use these slightly more verbose versions that emulate flatMap behavior. Client must support at least ES5, so no Internet Explorer 8 or below.
These will return the same result as above.
function flattenEntries([key, value]) {
if (typeof value !== 'object') {
return [ [ key, value ] ];
}
const nestedEntries = Object
.entries(value)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), []);
nestedEntries.unshift([ key, value ]);
return nestedEntries;
}
function sortedStringify(obj, sorter, indent = 2) {
const sortedKeys = Object
.entries(obj)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), [])
.sort(sorter || undefined)
.map(entry => entry[0]);
return JSON.stringify(obj, sortedKeys, indent);
}
An additional solution that works for nested objects as well:
const myFunc = (key) =>
JSON.stringify(key, (_, v) =>
v.constructor === Object ? Object.entries(v).sort() : v
);
const jsonFunc = JSON.stringify;
const obj1 = {
key1: "value1",
key2: {
key3: "value2",
key4: "value3",
},
};
const obj2 = {
key2: {
key4: "value3",
key3: "value2",
},
key1: "value1",
};
console.log(`JSON: ${jsonFunc(obj1) === jsonFunc(obj2)}`);
console.log(`My: ${myFunc(obj1) === myFunc(obj2)}`);
Works with lodash, nested objects, any value of object attribute:
function sort(myObj) {
var sortedObj = {};
Object.keys(myObj).sort().forEach(key => {
sortedObj[key] = _.isPlainObject(myObj[key]) ? sort(myObj[key]) : myObj[key]
})
return sortedObj;
}
JSON.stringify(sort(yourObj), null, 2)
It relies on Chrome's and Node's behaviour that the first key assigned to an object is outputted first by JSON.stringify.
After all, it needs an Array that caches all keys in the nested object (otherwise it will omit the uncached keys.) The oldest answer is just plain wrong, because second argument doesn't care about dot-notation. So, the answer (using Set) becomes.
function stableStringify (obj) {
const keys = new Set()
const getAndSortKeys = (a) => {
if (a) {
if (typeof a === 'object' && a.toString() === '[object Object]') {
Object.keys(a).map((k) => {
keys.add(k)
getAndSortKeys(a[k])
})
} else if (Array.isArray(a)) {
a.map((el) => getAndSortKeys(el))
}
}
}
getAndSortKeys(obj)
return JSON.stringify(obj, Array.from(keys).sort())
}
Try:
function obj(){
this.name = '';
this.os = '';
}
a = new obj();
a.name = 'X',
a.os = 'linux';
JSON.stringify(a);
b = new obj();
b.os = 'linux';
b.name = 'X',
JSON.stringify(b);
I made a function to sort object, and with callback .. which actually create a new object
function sortObj( obj , callback ) {
var r = [] ;
for ( var i in obj ){
if ( obj.hasOwnProperty( i ) ) {
r.push( { key: i , value : obj[i] } );
}
}
return r.sort( callback ).reduce( function( obj , n ){
obj[ n.key ] = n.value ;
return obj;
},{});
}
and call it with object .
var obj = {
name : "anu",
os : "windows",
value : 'msio',
};
var result = sortObj( obj , function( a, b ){
return a.key < b.key ;
});
JSON.stringify( result )
which prints {"value":"msio","os":"windows","name":"anu"} , and for sorting with value .
var result = sortObj( obj , function( a, b ){
return a.value < b.value ;
});
JSON.stringify( result )
which prints {"os":"windows","value":"msio","name":"anu"}
If objects in the list does not have same properties, generate a combined master object before stringify:
let arr=[ <object1>, <object2>, ... ]
let o = {}
for ( let i = 0; i < arr.length; i++ ) {
Object.assign( o, arr[i] );
}
JSON.stringify( arr, Object.keys( o ).sort() );
function FlatternInSort( obj ) {
if( typeof obj === 'object' )
{
if( obj.constructor === Object )
{ //here use underscore.js
let PaireStr = _( obj ).chain().pairs().sortBy( p => p[0] ).map( p => p.map( FlatternInSort ).join( ':' )).value().join( ',' );
return '{' + PaireStr + '}';
}
return '[' + obj.map( FlatternInSort ).join( ',' ) + ']';
}
return JSON.stringify( obj );
}
// example as below. in each layer, for objects like {}, flattened in key sort. for arrays, numbers or strings, flattened like/with JSON.stringify.
FlatternInSort( { c:9, b: { y: 4, z: 2, e: 9 }, F:4, a:[{j:8, h:3},{a:3,b:7}] } )
"{"F":4,"a":[{"h":3,"j":8},{"a":3,"b":7}],"b":{"e":9,"y":4,"z":2},"c":9}"
Extending AJP's answer, to handle arrays:
function sort(myObj) {
var sortedObj = {};
Object.keys(myObj).sort().forEach(key => {
sortedObj[key] = _.isPlainObject(myObj[key]) ? sort(myObj[key]) : _.isArray(myObj[key])? myObj[key].map(sort) : myObj[key]
})
return sortedObj;
}
Surprised nobody has mentioned lodash's isEqual function.
Performs a deep comparison between two values to determine if they are
equivalent.
Note: This method supports comparing arrays, array buffers, booleans,
date objects, error objects, maps, numbers, Object objects, regexes,
sets, strings, symbols, and typed arrays. Object objects are compared
by their own, not inherited, enumerable properties. Functions and DOM
nodes are compared by strict equality, i.e. ===.
https://lodash.com/docs/4.17.11#isEqual
With the original problem - keys being inconsistently ordered - it's a great solution - and of course it will just stop if it finds a conflict instead of blindly serializing the whole object.
To avoid importing the whole library you do this:
import { isEqual } from "lodash-es";
Bonus example:
You can also use this with RxJS with this custom operator
export const distinctUntilEqualChanged = <T>(): MonoTypeOperatorFunction<T> =>
pipe(distinctUntilChanged(isEqual));
Here is a clone approach...clone the object before converting to json:
function sort(o: any): any {
if (null === o) return o;
if (undefined === o) return o;
if (typeof o !== "object") return o;
if (Array.isArray(o)) {
return o.map((item) => sort(item));
}
const keys = Object.keys(o).sort();
const result = <any>{};
keys.forEach((k) => (result[k] = sort(o[k])));
return result;
}
If is very new but seems to work on package.json files fine.
Don't be confused with the object monitoring of Chrome debugger. It shows sorted keys in object, even though actually it is not sorted. You have to sort the object before you stringify it.
Before I found libs like fast-json-stable-stringify (haven't tested it in production myself), I was doing it this way:
import { flatten } from "flat";
import { set } from 'lodash/fp';
const sortJson = (jsonString) => {
const object = JSON.parse(jsonString);
const flatObject = flatten(object);
const propsSorted = Object.entries(flatObject).map(([key, value]) => ({ key, value })).sort((a, b) => a.key.localeCompare(b.key));
const objectSorted = propsSorted.reduce((object, { key, value }) => set(key, value, object), {});
return JSON.stringify(objectSorted);
};
const originalJson = JSON.stringify({ c: { z: 3, x: 1, y: 2 }, a: true, b: [ 'a', 'b', 'c' ] });
console.log(sortJson(originalJson)); // {"a":true,"b":["a","b","c"],"c":{"x":1,"y":2,"z":3}}
There is Array.sort method which can be helpful for you. For example:
yourBigArray.sort(function(a,b){
//custom sorting mechanism
});
I have the associative array:
array["sub2"] = 1;
array["sub0"] = -1;
array["sub1"] = 0;
array["sub3"] = 1;
array["sub4"] = 0;
What is the most elegant way to sort (descending) by its values where the result would be an array with the respective indices in this order:
sub2, sub3, sub1, sub4, sub0
Javascript doesn't have "associative arrays" the way you're thinking of them. Instead, you simply have the ability to set object properties using array-like syntax (as in your example), plus the ability to iterate over an object's properties.
The upshot of this is that there is no guarantee as to the order in which you iterate over the properties, so there is nothing like a sort for them. Instead, you'll need to convert your object properties into a "true" array (which does guarantee order). Here's a code snippet for converting an object into an array of two-tuples (two-element arrays), sorting it as you describe, then iterating over it:
var tuples = [];
for (var key in obj) tuples.push([key, obj[key]]);
tuples.sort(function(a, b) {
a = a[1];
b = b[1];
return a < b ? -1 : (a > b ? 1 : 0);
});
for (var i = 0; i < tuples.length; i++) {
var key = tuples[i][0];
var value = tuples[i][1];
// do something with key and value
}
You may find it more natural to wrap this in a function which takes a callback:
function bySortedValue(obj, callback, context) {
var tuples = [];
for (var key in obj) tuples.push([key, obj[key]]);
tuples.sort(function(a, b) {
return a[1] < b[1] ? 1 : a[1] > b[1] ? -1 : 0
});
var length = tuples.length;
while (length--) callback.call(context, tuples[length][0], tuples[length][1]);
}
bySortedValue({
foo: 1,
bar: 7,
baz: 3
}, function(key, value) {
document.getElementById('res').innerHTML += `${key}: ${value}<br>`
});
<p id='res'>Result:<br/><br/><p>
Instead of correcting you on the semantics of an 'associative array', I think this is what you want:
function getSortedKeys(obj) {
var keys = Object.keys(obj);
return keys.sort(function(a,b){return obj[b]-obj[a]});
}
for really old browsers, use this instead:
function getSortedKeys(obj) {
var keys = []; for(var key in obj) keys.push(key);
return keys.sort(function(a,b){return obj[b]-obj[a]});
}
You dump in an object (like yours) and get an array of the keys - eh properties - back, sorted descending by the (numerical) value of the, eh, values of the, eh, object.
This only works if your values are numerical. Tweek the little function(a,b) in there to change the sorting mechanism to work ascending, or work for string values (for example). Left as an exercise for the reader.
Continued discussion & other solutions covered at How to sort an (associative) array by value? with the best solution (for my case) being by saml (quoted below).
Arrays can only have numeric indexes. You'd need to rewrite this as either an Object, or an Array of Objects.
var status = new Array();
status.push({name: 'BOB', val: 10});
status.push({name: 'TOM', val: 3});
status.push({name: 'ROB', val: 22});
status.push({name: 'JON', val: 7});
If you like the status.push method, you can sort it with:
status.sort(function(a,b) {
return a.val - b.val;
});
There really isn't any such thing as an "associative array" in JavaScript. What you've got there is just a plain old object. They work kind-of like associative arrays, of course, and the keys are available but there's no semantics around the order of keys.
You could turn your object into an array of objects (key/value pairs) and sort that:
function sortObj(object, sortFunc) {
var rv = [];
for (var k in object) {
if (object.hasOwnProperty(k)) rv.push({key: k, value: object[k]});
}
rv.sort(function(o1, o2) {
return sortFunc(o1.key, o2.key);
});
return rv;
}
Then you'd call that with a comparator function.
The best approach for the specific case here, in my opinion, is the one commonpike suggested. A little improvement I'd suggest that works in modern browsers is:
// aao is the "associative array" you need to "sort"
Object.keys(aao).sort(function(a,b){return aao[b]-aao[a]});
This could apply easily and work great in the specific case here so you can do:
let aoo={};
aao["sub2"]=1;
aao["sub0"]=-1;
aao["sub1"]=0;
aao["sub3"]=1;
aao["sub4"]=0;
let sk=Object.keys(aao).sort(function(a,b){return aao[b]-aao[a]});
// now you can loop using the sorted keys in `sk` to do stuffs
for (let i=sk.length-1;i>=0;--i){
// do something with sk[i] or aoo[sk[i]]
}
Besides of this, I provide here a more "generic" function you can use to sort even in wider range of situations and that mixes the improvement I just suggested with the approaches of the answers by Ben Blank (sorting also string values) and PopeJohnPaulII (sorting by specific object field/property) and lets you decide if you want an ascendant or descendant order, here it is:
// aao := is the "associative array" you need to "sort"
// comp := is the "field" you want to compare or "" if you have no "fields" and simply need to compare values
// intVal := must be false if you need comparing non-integer values
// desc := set to true will sort keys in descendant order (default sort order is ascendant)
function sortedKeys(aao,comp="",intVal=false,desc=false){
let keys=Object.keys(aao);
if (comp!="") {
if (intVal) {
if (desc) return keys.sort(function(a,b){return aao[b][comp]-aao[a][comp]});
else return keys.sort(function(a,b){return aao[a][comp]-aao[a][comp]});
} else {
if (desc) return keys.sort(function(a,b){return aao[b][comp]<aao[a][comp]?1:aao[b][comp]>aao[a][comp]?-1:0});
else return keys.sort(function(a,b){return aao[a][comp]<aao[b][comp]?1:aao[a][comp]>aao[b][comp]?-1:0});
}
} else {
if (intVal) {
if (desc) return keys.sort(function(a,b){return aao[b]-aao[a]});
else return keys.sort(function(a,b){return aao[a]-aao[b]});
} else {
if (desc) return keys.sort(function(a,b){return aao[b]<aao[a]?1:aao[b]>aao[a]?-1:0});
else return keys.sort(function(a,b){return aao[a]<aao[b]?1:aao[a]>aao[b]?-1:0});
}
}
}
You can test the functionalities trying something like the following code:
let items={};
items['Edward']=21;
items['Sharpe']=37;
items['And']=45;
items['The']=-12;
items['Magnetic']=13;
items['Zeros']=37;
//equivalent to:
//let items={"Edward": 21, "Sharpe": 37, "And": 45, "The": -12, ...};
console.log("1: "+sortedKeys(items));
console.log("2: "+sortedKeys(items,"",false,true));
console.log("3: "+sortedKeys(items,"",true,false));
console.log("4: "+sortedKeys(items,"",true,true));
/* OUTPUT
1: And,Sharpe,Zeros,Edward,Magnetic,The
2: The,Magnetic,Edward,Sharpe,Zeros,And
3: The,Magnetic,Edward,Sharpe,Zeros,And
4: And,Sharpe,Zeros,Edward,Magnetic,The
*/
items={};
items['k1']={name:'Edward',value:21};
items['k2']={name:'Sharpe',value:37};
items['k3']={name:'And',value:45};
items['k4']={name:'The',value:-12};
items['k5']={name:'Magnetic',value:13};
items['k6']={name:'Zeros',value:37};
console.log("1: "+sortedKeys(items,"name"));
console.log("2: "+sortedKeys(items,"name",false,true));
/* OUTPUT
1: k6,k4,k2,k5,k1,k3
2: k3,k1,k5,k2,k4,k6
*/
As I already said, you can loop over sorted keys if you need doing stuffs
let sk=sortedKeys(aoo);
// now you can loop using the sorted keys in `sk` to do stuffs
for (let i=sk.length-1;i>=0;--i){
// do something with sk[i] or aoo[sk[i]]
}
Last, but not least, some useful references to Object.keys and Array.sort
Here is a variation of ben blank's answer, if you don't like tuples.
This saves you a few characters.
var keys = [];
for (var key in sortme) {
keys.push(key);
}
keys.sort(function(k0, k1) {
var a = sortme[k0];
var b = sortme[k1];
return a < b ? -1 : (a > b ? 1 : 0);
});
for (var i = 0; i < keys.length; ++i) {
var key = keys[i];
var value = sortme[key];
// Do something with key and value.
}
No unnecessary complication required...
function sortMapByValue(map)
{
var tupleArray = [];
for (var key in map) tupleArray.push([key, map[key]]);
tupleArray.sort(function (a, b) { return a[1] - b[1] });
return tupleArray;
}
i use $.each of jquery but you can make it with a for loop, an improvement is this:
//.ArraySort(array)
/* Sort an array
*/
ArraySort = function(array, sortFunc){
var tmp = [];
var aSorted=[];
var oSorted={};
for (var k in array) {
if (array.hasOwnProperty(k))
tmp.push({key: k, value: array[k]});
}
tmp.sort(function(o1, o2) {
return sortFunc(o1.value, o2.value);
});
if(Object.prototype.toString.call(array) === '[object Array]'){
$.each(tmp, function(index, value){
aSorted.push(value.value);
});
return aSorted;
}
if(Object.prototype.toString.call(array) === '[object Object]'){
$.each(tmp, function(index, value){
oSorted[value.key]=value.value;
});
return oSorted;
}
};
So now you can do
console.log("ArraySort");
var arr1 = [4,3,6,1,2,8,5,9,9];
var arr2 = {'a':4, 'b':3, 'c':6, 'd':1, 'e':2, 'f':8, 'g':5, 'h':9};
var arr3 = {a: 'green', b: 'brown', c: 'blue', d: 'red'};
var result1 = ArraySort(arr1, function(a,b){return a-b});
var result2 = ArraySort(arr2, function(a,b){return a-b});
var result3 = ArraySort(arr3, function(a,b){return a>b});
console.log(result1);
console.log(result2);
console.log(result3);
Just so it's out there and someone is looking for tuple based sorts.
This will compare the first element of the object in array, than the second element and so on. i.e in the example below, it will compare first by "a", then by "b" and so on.
let arr = [
{a:1, b:2, c:3},
{a:3, b:5, c:1},
{a:2, b:3, c:9},
{a:2, b:5, c:9},
{a:2, b:3, c:10}
]
function getSortedScore(obj) {
var keys = [];
for(var key in obj[0]) keys.push(key);
return obj.sort(function(a,b){
for (var i in keys) {
let k = keys[i];
if (a[k]-b[k] > 0) return -1;
else if (a[k]-b[k] < 0) return 1;
else continue;
};
});
}
console.log(getSortedScore(arr))
OUPUTS
[ { a: 3, b: 5, c: 1 },
{ a: 2, b: 5, c: 9 },
{ a: 2, b: 3, c: 10 },
{ a: 2, b: 3, c: 9 },
{ a: 1, b: 2, c: 3 } ]
A modern approuch to this:
Object.fromEntries(Object.entries(data).sort((a,b)=>b[1]-a[1]).slice(0,5))
P.S: I did an optional slice, you can remove it if you want.
#commonpike's answer is "the right one", but as he goes on to comment...
most browsers nowadays just support Object.keys()
Yeah.. Object.keys() is WAY better.
But what's even better? Duh, it's it in coffeescript!
sortedKeys = (x) -> Object.keys(x).sort (a,b) -> x[a] - x[b]
sortedKeys
'a' : 1
'b' : 3
'c' : 4
'd' : -1
[ 'd', 'a', 'b', 'c' ]
I have an object that I'm iterating
for (el in object) {
// Some work here
}
I want to know when is the last iteration, inside the iteration, so I can do
for (el in object) {
// Some work here
if (last_iteration) {
// Do something
}
}
Any straightforward way to do it?
I know I'm late but I just ran into this and fixed it like this:
let i = 0;
const object = { a: 1, b: 2 };
const length = Object.keys(object).length;
for (el in object) {
const last = i === length - 1; // true if last, false if not last
console.log(i, el, last);
i++;
}
Update: A few years later, i++ at the end of a loop really irks me.
const object = { a: 1, b: 2 };
const length = Object.keys(object).length;
for (const [key, isLast] of Object.keys(object)
.map((key, i) => [key, i === length - 1])) {
console.log(key, isLast);
}
or
const object = { a: 1, b: 2 };
const length = Object.keys(object).length;
Object.keys(object)
.map((key, i) => [key, i === length - 1]))
.map(([key, isLast]) => {
console.log(key, isLast);
})
You can do something like this:
var first = true;
var prev;
for (var el in object) {
// Some work here
if (first) {
first = false;
} else {
doSomething(prev, object[prev]);
}
prev = el;
}
if (prev !== undefined) { // There was at least one element
doSomethingElse(prev, object[prev]); // Prev is now last of all elements
}
This is in case you want to process all but the last element in one way (doSomething) and process the last element in another way (doSomethingElse).
If you want to process all the elements in one way (doSomething) and want to have extra processing for the last element only (doSomethingExtra), you can do:
var prev;
for (var el in object) {
// Some work here
doSomething(el, object[el]);
prev = el;
}
if (prev !== undefined) { // There was at least one element
doSomethingExtra(prev, object[prev]); // Prev is now last of all elements
}
To make it even shorter, you can do similar to what Török Gábor did in the gist he provided, by reusing el variable, i.e.:
var el;
for (el in object) {
// Some work here
doSomething(el, object[el]);
}
if (el !== undefined) { // There was at least one element
doSomethingExtra(el, object[el]); // El is now last of all elements
}
Hope this helps.
If the keys are not numerical, this works:
let anObject = {'one': 1, 'two': 2, 'three': 3, 'lastKey': 4};
let objectKeys = Object.keys(anObject);
let lastObjectKey = objectKeys.slice(-1).toString();
console.log(lastObjectKey); // 'lastKey'
The Object.keys() method returns an array of a given object's own enumerable property names, iterated in the same order that a normal loop would.
Example with numerical keys causing reordering:
let anObject2 = {3: 3, 2: 2, 'notLastKey': 4, 1: 'lastKey'};
let objectKeys2 = Object.keys(anObject2);
console.log(objectKeys2); // ["1", "2", "3", "notLastKey"]
let lastObjectKey2 = objectKeys2.slice(-1).toString();
console.log(lastObjectKey2); // "notLastKey"
Note that this will only work if the object you are iterating over is an array (has numeric keys)
var a = [1,2,3,4,5];
for (i in a) {
if(a[+i+1] === undefined)
console.log('the last one is: ' + a[i]);
}
Note that the + sign before i is necessary since if omitted, it will do a string concatenation, the keys resulting in 01, 12, 23, etc
as said already, there is no distinct order for properties, so last enumerated property is only known afterwards.
var object = { a: 'b', c: 42 };
for ( var string in object ) ;
alert( object[string] ); // last property name is still here