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I have string like the following:
11222233344444445666
What I would like to do is output the number followed the times it was displayed:
112433475163
Question is, I want this to be efficient. I can store this in an object as the following:
1: { id: 1, displayed: 2},
2: { id: 2, displayed: 1},
3: { id: 3, displayed: 2},
etc.
I can access this object and increment displayed.
My issues is, there is no guarantee in the order. I would like to store the keys in the order they are in the string. How do I accomplish the importance of the order in the object?
This is a proposal for run length coding with an array which holds infomation about one charcter and the count of it:
{
"char": "1",
"count": 2
},
var string = "11222233344444445666",
array = function () {
var r = [], o = {};
string.split('').forEach(function (a, i, aa) {
if (a !== aa[i - 1]) {
o[a] = { char: a, count: 0 };
r.push(o[a]);
}
o[a].count++;
});
return r;
}(string);
document.write('<pre>' + JSON.stringify(array, 0, 4) + '</pre>');
Quick solution with for loop:
var str = "7771122229933344444445666",
obj = {},
len = str.length,
val = null,
count_str = "",
key = "";
for (var i = 0; i < len; i++) {
val = str[i], key = 'k' + val;
if (!obj[key]) {
obj[key] = {'id': val, 'displayed': 1};
} else {
obj[key].displayed++;
}
}
for (var p in obj) {
count_str += obj[p]['id'] + obj[p]['displayed'];
}
console.log(count_str); // "7312249233475163"
because you have such a small set of distinct numbers, I seen no reason why you can't use a array (yeah it's not super ideal memorywise if you skip values and it becomes sparse, but for such a small subset it won't affect you enough to worry of it). Then you can use (number-1) as the index and increment that number as needed.
var counts = [];
var str = "11222233344444445666";
for(var i in str){
var index = parseInt(str[i])-1
counts[index] = (counts[index]||0)+1;
}
for(var i in counts){
var which = 1+parseInt(i);
var count = counts[i];
console.log("# of " + which +"'s: "+count);
}
https://jsfiddle.net/ga0fqpqn/
note: You shouldn't need the parseInt(i)... just +i should work but I think jsfiddle has a bug with it about it defaulting i to handle like a string.
You could store an additional array with the order of the numbers, which you only append to if the object doesn't yet contain the given number. Then once you're done counting, iterate through that array and output the number and the count from the lookup dictionary.
var chars = "1234576123452345".split("");
var order = [];
var hash = {};
chars.forEach(function(char) {
if (!hash[char]) {
hash[char] = 1;
order.push(char);
} else {
hash[char]++;
}
});
console.log(order.map(function(char) {
return char + hash[char];
}).join(""));
// "12233343537161"
I have an array of objects like so:
var objects = [{a:'b',c:'d',count:1},{a:'b',c:'d',count:2},{a:'y',c:'d',count:4}]
I want to sum all the counts that have the same a and b values to make something like so:
{a:'b',c:'d',count:3},{a:'y',c:'d',count:4}
Is there an easy way to do this?
For that case, you could easily group your objects by the value of a + b:
var objects = [{a:'b',c:'d',count:1},{a:'b',c:'d',count:2},{a:'y',c:'d',count:4}]
function getId(obj){ // how to group the objects
return obj.a + '|'+ obj.c
}
var groups = {};
for(var i=0;i<objects.length;i++){ // for each obj
var id = getId(objects[i]) // get id
if(groups.hasOwnProperty(id)){ // if group is already created, add count
groups[id].count += objects[i].count
}else{ // else create group with same values
groups[id] = {a:objects[i].a, c: objects[i].c, count:objects[i].count}
}
}
console.log(groups) // you can then change the groups to an array if you want
There's a great library called ramda which is wonderful for composing complicated data manipulation:
var R = require('ramda'); // Edit: you can also use a script tag if you're working in the browser. see http://ramdajs.com/
// Concatenate the values for a & c so that we group by values
var groups = R.groupBy(R.converge(R.concat, R.prop('a'), R.prop('c')), objects);
// We just want the grouped arrays, not the concatenated keys
groups = R.values(groups);
var aggregateCounts = R.compose(R.sum, R.pluck('count'));
groups = groups.map(function(group) {
return {
a: group[0].a,
c: group[0].c,
count: aggregateCounts(group)
};
});
Just group them by the keys:
var aggregate = function (objects) {
var map = {}; // map to store data
var a = []; // temporary array to hold the objects
objects.forEach(function (d) {
var key = d.a > d.c ? String(d.c) + d.a : String(d.a) + d.c;
// if {a:2,c:3} is the same as {c:2,a:3}, use the above,
// otherwise, just use key = String(d.a) + String(d.c);
map[key] = (map[key] || 0) + d.count;
})
// e.g., key === "bd"
for (var key in map) {
// so split it into ["b", "d"]
var k = key.toString().split("");
// and push it to the temp array as the appropriate object
a.push({ a: k[0], c: k[1], count: map[key] });
}
return a;
}
var objects = [{a:'b',c:'d',count:1},{a:'b',c:'d',count:2},{a:'y',c:'d',count:4}];
console.log(aggregate(objects));
// [{a:"b",c:"d",count:3},{a:"d",c:"y",count:4}]
You could sort the objects array, then create a new array by pushing the objects as a and c change:
var objects = [{a:'b',c:'d',count:1},{a:'y',c:'d',count:4},{a:'b',c:'d',count:2}],
newobj = [];
objects.sort(function(a,b) {
return a.a+a.c > b.a+b.c ? 1 :
a.a+a.c < b.a+b.c ? -1 :
0;
});
for(var i = 0 ; i < objects.length ; i++) {
if(i === 0 || objects[i].a !== objects[i-1].a || objects[i].b !== objects[i-1].b) {
newobj.push({a: objects[i].a, c: objects[i].c, count: objects[i].count});
}
else {
newobj[newobj.length-1].count+= objects[i].count;
}
}
alert(JSON.stringify(newobj));
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!
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 two arrays of JavaScript Objects that I'd like to compare to see if they are the same. The objects may not (and most likely will not) be in the same order in each array. Each array shouldn't have any more than 10 objects. I thought jQuery might have an elegant solution to this problem, but I wasn't able to find much online.
I know that a brute nested $.each(array, function(){}) solution could work, but is there any built in function that I'm not aware of?
Thanks.
There is an easy way...
$(arr1).not(arr2).length === 0 && $(arr2).not(arr1).length === 0
If the above returns true, both the arrays are same even if the elements are in different order.
NOTE: This works only for jquery versions < 3.0.0 when using JSON objects
I was also looking for this today and found:
http://www.breakingpar.com/bkp/home.nsf/0/87256B280015193F87256BFB0077DFFD
Don't know if that's a good solution though they do mention some performance considerations taken into account.
I like the idea of a jQuery helper method.
#David I'd rather see your compare method to work like:
jQuery.compare(a, b)
I doesn't make sense to me to be doing:
$(a).compare(b)
where a and b are arrays. Normally when you $(something) you'd be passing a selector string to work with DOM elements.
Also regarding sorting and 'caching' the sorted arrays:
I don't think sorting once at the start of the method instead of every time through the loop is 'caching'. The sort will still happen every time you call compare(b). That's just semantics, but...
for (var i = 0; t[i]; i++) { ...this loop finishes early if your t array contains a false value in it somewhere, so $([1, 2, 3, 4]).compare([1, false, 2, 3]) returns true!
More importantly the array sort() method sorts the array in place, so doing var b = t.sort() ...doesn't create a sorted copy of the original array, it sorts the original array and also assigns a reference to it in b. I don't think the compare method should have side-effects.
It seems what we need to do is to copy the arrays before working on them. The best answer I could find for how to do that in a jQuery way was by none other than John Resig here on SO! What is the most efficient way to deep clone an object in JavaScript? (see comments on his answer for the array version of the object cloning recipe)
In which case I think the code for it would be:
jQuery.extend({
compare: function (arrayA, arrayB) {
if (arrayA.length != arrayB.length) { return false; }
// sort modifies original array
// (which are passed by reference to our method!)
// so clone the arrays before sorting
var a = jQuery.extend(true, [], arrayA);
var b = jQuery.extend(true, [], arrayB);
a.sort();
b.sort();
for (var i = 0, l = a.length; i < l; i++) {
if (a[i] !== b[i]) {
return false;
}
}
return true;
}
});
var a = [1, 2, 3];
var b = [2, 3, 4];
var c = [3, 4, 2];
jQuery.compare(a, b);
// false
jQuery.compare(b, c);
// true
// c is still unsorted [3, 4, 2]
My approach was quite different - I flattened out both collections using JSON.stringify and used a normal string compare to check for equality.
I.e.
var arr1 = [
{Col: 'a', Val: 1},
{Col: 'b', Val: 2},
{Col: 'c', Val: 3}
];
var arr2 = [
{Col: 'x', Val: 24},
{Col: 'y', Val: 25},
{Col: 'z', Val: 26}
];
if(JSON.stringify(arr1) == JSON.stringify(arr2)){
alert('Collections are equal');
}else{
alert('Collections are not equal');
}
NB: Please note that his method assumes that both Collections are sorted in a similar fashion, if not, it would give you a false result!
Convert both array to string and compare
if (JSON.stringify(array1) == JSON.stringify(array2))
{
// your code here
}
I found this discussion because I needed a way to deep compare arrays and objects. Using the examples here, I came up with the following (broken up into 3 methods for clarity):
jQuery.extend({
compare : function (a,b) {
var obj_str = '[object Object]',
arr_str = '[object Array]',
a_type = Object.prototype.toString.apply(a),
b_type = Object.prototype.toString.apply(b);
if ( a_type !== b_type) { return false; }
else if (a_type === obj_str) {
return $.compareObject(a,b);
}
else if (a_type === arr_str) {
return $.compareArray(a,b);
}
return (a === b);
}
});
jQuery.extend({
compareArray: function (arrayA, arrayB) {
var a,b,i,a_type,b_type;
// References to each other?
if (arrayA === arrayB) { return true;}
if (arrayA.length != arrayB.length) { return false; }
// sort modifies original array
// (which are passed by reference to our method!)
// so clone the arrays before sorting
a = jQuery.extend(true, [], arrayA);
b = jQuery.extend(true, [], arrayB);
a.sort();
b.sort();
for (i = 0, l = a.length; i < l; i+=1) {
a_type = Object.prototype.toString.apply(a[i]);
b_type = Object.prototype.toString.apply(b[i]);
if (a_type !== b_type) {
return false;
}
if ($.compare(a[i],b[i]) === false) {
return false;
}
}
return true;
}
});
jQuery.extend({
compareObject : function(objA,objB) {
var i,a_type,b_type;
// Compare if they are references to each other
if (objA === objB) { return true;}
if (Object.keys(objA).length !== Object.keys(objB).length) { return false;}
for (i in objA) {
if (objA.hasOwnProperty(i)) {
if (typeof objB[i] === 'undefined') {
return false;
}
else {
a_type = Object.prototype.toString.apply(objA[i]);
b_type = Object.prototype.toString.apply(objB[i]);
if (a_type !== b_type) {
return false;
}
}
}
if ($.compare(objA[i],objB[i]) === false){
return false;
}
}
return true;
}
});
Testing
var a={a : {a : 1, b: 2}},
b={a : {a : 1, b: 2}},
c={a : {a : 1, b: 3}},
d=[1,2,3],
e=[2,1,3];
console.debug('a and b = ' + $.compare(a,b)); // a and b = true
console.debug('b and b = ' + $.compare(b,b)); // b and b = true
console.debug('b and c = ' + $.compare(b,c)); // b and c = false
console.debug('c and d = ' + $.compare(c,d)); // c and d = false
console.debug('d and e = ' + $.compare(d,e)); // d and e = true
In my case compared arrays contain only numbers and strings. This solution worked for me:
function are_arrs_equal(arr1, arr2){
return arr1.sort().toString() === arr2.sort().toString()
}
Let's test it!
arr1 = [1, 2, 3, 'nik']
arr2 = ['nik', 3, 1, 2]
arr3 = [1, 2, 5]
console.log (are_arrs_equal(arr1, arr2)) //true
console.log (are_arrs_equal(arr1, arr3)) //false
I don't think there's a good "jQuery " way to do this, but if you need efficiency, map one of the arrays by a certain key (one of the unique object fields), and then do comparison by looping through the other array and comparing against the map, or associative array, you just built.
If efficiency is not an issue, just compare every object in A to every object in B. As long as |A| and |B| are small, you should be okay.
Well, if you want to compare only the contents of arrays, there's a useful jQuery function $.inArray()
var arr = [11, "String #1", 14, "String #2"];
var arr_true = ["String #1", 14, "String #2", 11]; // contents are the same as arr
var arr_false = ["String #1", 14, "String #2", 16]; // contents differ
function test(arr_1, arr_2) {
var equal = arr_1.length == arr_2.length; // if array sizes mismatches, then we assume, that they are not equal
if (equal) {
$.each(arr_1, function (foo, val) {
if (!equal) return false;
if ($.inArray(val, arr_2) == -1) {
equal = false;
} else {
equal = true;
}
});
}
return equal;
}
alert('Array contents are the same? ' + test(arr, arr_true)); //- returns true
alert('Array contents are the same? ' + test(arr, arr_false)); //- returns false
Change array to string and compare
var arr = [1,2,3],
arr2 = [1,2,3];
console.log(arr.toString() === arr2.toString());
The nice one liner from Sudhakar R as jQuery global method.
/**
* Compare two arrays if they are equal even if they have different order.
*
* #link https://stackoverflow.com/a/7726509
*/
jQuery.extend({
/**
* #param {array} a
* First array to compare.
* #param {array} b
* Second array to compare.
* #return {boolean}
* True if both arrays are equal, otherwise false.
*/
arrayCompare: function (a, b) {
return $(a).not(b).get().length === 0 && $(b).not(a).get().length === 0;
}
});
I also found this when looking to do some array comparisons with jQuery. In my case I had strings which I knew to be arrays:
var needle = 'apple orange';
var haystack = 'kiwi orange banana apple plum';
But I cared if it was a complete match or only a partial match, so I used something like the following, based off of Sudhakar R's answer:
function compareStrings( needle, haystack ){
var needleArr = needle.split(" "),
haystackArr = haystack.split(" "),
compare = $(haystackArr).not(needleArr).get().length;
if( compare == 0 ){
return 'all';
} else if ( compare == haystackArr.length ) {
return 'none';
} else {
return 'partial';
}
}
If duplicates matter such that [1, 1, 2] should not be equal to [2, 1] but should equal [1, 2, 1], here is a reference counting solution:
const arrayContentsEqual = (arrayA, arrayB) => {
if (arrayA.length !== arrayB.length) {
return false}
const refCount = (function() {
const refCountMap = {};
const refCountFn = (elt, count) => {
refCountMap[elt] = (refCountMap[elt] || 0) + count}
refCountFn.isZero = () => {
for (let elt in refCountMap) {
if (refCountMap[elt] !== 0) {
return false}}
return true}
return refCountFn})()
arrayB.map(eltB => refCount(eltB, 1));
arrayA.map(eltA => refCount(eltA, -1));
return refCount.isZero()}
Here is the fiddle to play with.
var arr1 = [
{name: 'a', Val: 1},
{name: 'b', Val: 2},
{name: 'c', Val: 3}
];
var arr2 = [
{name: 'c', Val: 3},
{name: 'x', Val: 4},
{name: 'y', Val: 5},
{name: 'z', Val: 6}
];
var _isEqual = _.intersectionWith(arr1, arr2, _.isEqual);// common in both array
var _difference1 = _.differenceWith(arr1, arr2, _.isEqual);//difference from array1
var _difference2 = _.differenceWith(arr2, arr1, _.isEqual);//difference from array2
console.log(_isEqual);// common in both array
console.log(_difference1);//difference from array1
console.log(_difference2);//difference from array2
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.js"></script>
Try this
function check(c,d){
var a = c, b = d,flg = 0;
if(a.length == b.length)
{
for(var i=0;i<a.length;i++)
a[i] != b[i] ? flg++ : 0;
}
else
{
flg = 1;
}
return flg = 0;
}