比较 JavaScript 中的对象数组

Question

I want to compare 2 arrays of objects in JavaScript code. The objects have 8 total properties, but each object will not have a value for each, and the arrays are never going to be any larger than 8 items each, so maybe the brute force method of traversing each and then looking at the values of the 8 properties is the easiest way to do what I want to do, but before implementing, I wanted to see if anyone had a more elegant solution. Any thoughts?

Answer 1

As serialization doesn't work generally (only when the order of properties matches: JSON.stringify({a:1,b:2}) !== JSON.stringify({b:2,a:1}) ) you have to check the count of properties and compare each property as well:

 const objectsEqual = (o1, o2) => Object.keys(o1).length === Object.keys(o2).length && Object.keys(o1).every(p => o1[p] === o2[p]); const obj1 = { name: 'John', age: 33}; const obj2 = { age: 33, name: 'John' }; const obj3 = { name: 'John', age: 45 }; console.log(objectsEqual(obj1, obj2)); // true console.log(objectsEqual(obj1, obj3)); // false

If you need a deep comparison, you can call the function recursively:

 const obj1 = { name: 'John', age: 33, info: { married: true, hobbies: ['sport', 'art'] } }; const obj2 = { age: 33, name: 'John', info: { hobbies: ['sport', 'art'], married: true } }; const obj3 = { name: 'John', age: 33 }; const objectsEqual = (o1, o2) => typeof o1 === 'object' && Object.keys(o1).length > 0 ? Object.keys(o1).length === Object.keys(o2).length && Object.keys(o1).every(p => objectsEqual(o1[p], o2[p])) : o1 === o2; console.log(objectsEqual(obj1, obj2)); // true console.log(objectsEqual(obj1, obj3)); // false

Then it's easy to use this function to compare objects in arrays:

const arr1 = [obj1, obj1];
const arr2 = [obj1, obj2];
const arr3 = [obj1, obj3];

const arraysEqual = (a1, a2) => 
   a1.length === a2.length && a1.every((o, idx) => objectsEqual(o, a2[idx]));

console.log(arraysEqual(arr1, arr2)); // true
console.log(arraysEqual(arr1, arr3)); // false

Answer 2

EDIT: You cannot overload operators in current, common browser-based implementations of JavaScript interpreters.

To answer the original question, one way you could do this, and mind you, this is a bit of a hack, simply serialize the two arrays to JSON and then compare the two JSON strings. That would simply tell you if the arrays are different, obviously you could do this to each of the objects within the arrays as well to see which ones were different.

Another option is to use a library which has some nice facilities for comparing objects - I use and recommend MochiKit .

---

EDIT: The answer kamens gave deserves consideration as well, since a single function to compare two given objects would be much smaller than any library to do what I suggest (although my suggestion would certainly work well enough).

Here is a naïve implemenation that may do just enough for you - be aware that there are potential problems with this implementation:

function objectsAreSame(x, y) {
   var objectsAreSame = true;
   for(var propertyName in x) {
      if(x[propertyName] !== y[propertyName]) {
         objectsAreSame = false;
         break;
      }
   }
   return objectsAreSame;
}

The assumption is that both objects have the same exact list of properties.

Oh, and it is probably obvious that, for better or worse, I belong to the only-one-return-point camp. :)

Answer 3

Honestly, with 8 objects max and 8 properties max per object, your best bet is to just traverse each object and make the comparisons directly. It'll be fast and it'll be easy.

If you're going to be using these types of comparisons often, then I agree with Jason about JSON serialization...but otherwise there's no need to slow down your app with a new library or JSON serialization code.

Answer 4

I know this is an old question and the answers provided work fine ... but this is a bit shorter and doesn't require any additional libraries ( ie JSON ):

function arraysAreEqual(ary1,ary2){
  return (ary1.join('') == ary2.join(''));
}

Answer 5

I have worked a bit on a simple algorithm to compare contents of two objects and return an intelligible list of difference. Thought I would share. It borrows some ideas for jQuery, namely the map function implementation and the object and array type checking.

It returns a list of "diff objects", which are arrays with the diff info. It's very simple.

Here it is:

// compare contents of two objects and return a list of differences
// returns an array where each element is also an array in the form:
// [accessor, diffType, leftValue, rightValue ]
//
// diffType is one of the following:
//   value: when primitive values at that index are different
//   undefined: when values in that index exist in one object but don't in 
//              another; one of the values is always undefined
//   null: when a value in that index is null or undefined; values are
//         expressed as boolean values, indicated wheter they were nulls
//   type: when values in that index are of different types; values are 
//         expressed as types
//   length: when arrays in that index are of different length; values are
//           the lengths of the arrays
//

function DiffObjects(o1, o2) {
    // choose a map() impl.
    // you may use $.map from jQuery if you wish
    var map = Array.prototype.map?
        function(a) { return Array.prototype.map.apply(a, Array.prototype.slice.call(arguments, 1)); } :
        function(a, f) { 
            var ret = new Array(a.length), value;
            for ( var i = 0, length = a.length; i < length; i++ ) 
                ret[i] = f(a[i], i);
            return ret.concat();
        };

    // shorthand for push impl.
    var push = Array.prototype.push;

    // check for null/undefined values
    if ((o1 == null) || (o2 == null)) {
        if (o1 != o2)
            return [["", "null", o1!=null, o2!=null]];

        return undefined; // both null
    }
    // compare types
    if ((o1.constructor != o2.constructor) ||
        (typeof o1 != typeof o2)) {
        return [["", "type", Object.prototype.toString.call(o1), Object.prototype.toString.call(o2) ]]; // different type

    }

    // compare arrays
    if (Object.prototype.toString.call(o1) == "[object Array]") {
        if (o1.length != o2.length) { 
            return [["", "length", o1.length, o2.length]]; // different length
        }
        var diff =[];
        for (var i=0; i<o1.length; i++) {
            // per element nested diff
            var innerDiff = DiffObjects(o1[i], o2[i]);
            if (innerDiff) { // o1[i] != o2[i]
                // merge diff array into parent's while including parent object name ([i])
                push.apply(diff, map(innerDiff, function(o, j) { o[0]="[" + i + "]" + o[0]; return o; }));
            }
        }
        // if any differences were found, return them
        if (diff.length)
            return diff;
        // return nothing if arrays equal
        return undefined;
    }

    // compare object trees
    if (Object.prototype.toString.call(o1) == "[object Object]") {
        var diff =[];
        // check all props in o1
        for (var prop in o1) {
            // the double check in o1 is because in V8 objects remember keys set to undefined 
            if ((typeof o2[prop] == "undefined") && (typeof o1[prop] != "undefined")) {
                // prop exists in o1 but not in o2
                diff.push(["[" + prop + "]", "undefined", o1[prop], undefined]); // prop exists in o1 but not in o2

            }
            else {
                // per element nested diff
                var innerDiff = DiffObjects(o1[prop], o2[prop]);
                if (innerDiff) { // o1[prop] != o2[prop]
                    // merge diff array into parent's while including parent object name ([prop])
                    push.apply(diff, map(innerDiff, function(o, j) { o[0]="[" + prop + "]" + o[0]; return o; }));
                }

            }
        }
        for (var prop in o2) {
            // the double check in o2 is because in V8 objects remember keys set to undefined 
            if ((typeof o1[prop] == "undefined") && (typeof o2[prop] != "undefined")) {
                // prop exists in o2 but not in o1
                diff.push(["[" + prop + "]", "undefined", undefined, o2[prop]]); // prop exists in o2 but not in o1

            }
        }
        // if any differences were found, return them
        if (diff.length)
            return diff;
        // return nothing if objects equal
        return undefined;
    }
    // if same type and not null or objects or arrays
    // perform primitive value comparison
    if (o1 != o2)
        return [["", "value", o1, o2]];

    // return nothing if values are equal
    return undefined;
}

Answer 6

I tried JSON.stringify() and worked for me.

let array1 = [1,2,{value:'alpha'}] , array2 = [{value:'alpha'},'music',3,4];

JSON.stringify(array1) // "[1,2,{"value":"alpha"}]"

JSON.stringify(array2) // "[{"value":"alpha"},"music",3,4]"

JSON.stringify(array1) === JSON.stringify(array2); // false

Answer 7

There is a optimized code for case when function needs to equals to empty arrays (and returning false in that case)

const objectsEqual = (o1, o2) => {
    if (o2 === null && o1 !== null) return false;
    return o1 !== null && typeof o1 === 'object' && Object.keys(o1).length > 0 ?
        Object.keys(o1).length === Object.keys(o2).length && 
        Object.keys(o1).every(p => objectsEqual(o1[p], o2[p]))
        : (o1 !== null && Array.isArray(o1) && Array.isArray(o2) && !o1.length && 
        !o2.length) ? true : o1 === o2;
}

Answer 8

Here is my attempt, using Node's assert module + npm package object-hash .

I suppose that you would like to check if two arrays contain the same objects, even if those objects are ordered differently between the two arrays.

var assert = require('assert');
var hash = require('object-hash');

var obj1 = {a: 1, b: 2, c: 333},
    obj2 = {b: 2, a: 1, c: 444},
    obj3 = {b: "AAA", c: 555},
    obj4 = {c: 555, b: "AAA"};

var array1 = [obj1, obj2, obj3, obj4];
var array2 = [obj3, obj2, obj4, obj1]; // [obj3, obj3, obj2, obj1] should work as well

// calling assert.deepEquals(array1, array2) at this point FAILS (throws an AssertionError)
// even if array1 and array2 contain the same objects in different order,
// because array1[0].c !== array2[0].c

// sort objects in arrays by their hashes, so that if the arrays are identical,
// their objects can be compared in the same order, one by one
var array1 = sortArrayOnHash(array1);
var array2 = sortArrayOnHash(array2);

// then, this should output "PASS"
try {
    assert.deepEqual(array1, array2);
    console.log("PASS");
} catch (e) {
    console.log("FAIL");
    console.log(e);
}

// You could define as well something like Array.prototype.sortOnHash()...
function sortArrayOnHash(array) {
    return array.sort(function(a, b) {
        return hash(a) > hash(b);
    });
}

Answer 9

My practice implementation with sorting, tested and working.

const obj1 = { name: 'John', age: 33};
const obj2 = { age: 33, name: 'John' };
const obj3 = { name: 'John', age: 45 };

const equalObjs = ( obj1, obj2 ) => {
let keyExist = false;
for ( const [key, value] of Object.entries(obj1) ) {
     // Search each key in reference object and attach a callback function to 
     // compare the two object keys
    if( Object.keys(obj2).some( ( e ) => e == key ) ) {
        keyExist = true;
    }
}

return keyExist;

}


console.info( equalObjs( obj1, obj2 ) );

Compare your arrays

// Sort Arrays
    var arr1 = arr1.sort(( a, b ) => {
    var fa = Object.keys(a);
    var fb = Object.keys(b);

    if (fa < fb) {
        return -1;
    }
    if (fa > fb) {
        return 1;
    }
    return 0;
});

var arr2 = arr2.sort(( a, b ) => {
    var fa = Object.keys(a);
    var fb = Object.keys(b);

    if (fa < fb) {
        return -1;
    }
    if (fa > fb) {
        return 1;
    }
    return 0;
});

const equalArrays = ( arr1, arr2 ) => {
    // If the arrays are different length we an eliminate immediately
    if( arr1.length !== arr2.length ) {
        return false;
    } else if ( arr1.every(( obj, index ) => equalObjs( obj, arr2[index] ) ) ) {
        return true;
      } else { 
        return false;
      }
    }

    console.info( equalArrays( arr1, arr2 ) );

Answer 10

Please try this one:

function used_to_compare_two_arrays(a, b)
{
  // This block will make the array of indexed that array b contains a elements
  var c = a.filter(function(value, index, obj) {
    return b.indexOf(value) > -1;
  });

  // This is used for making comparison that both have same length if no condition go wrong 
  if (c.length !== a.length) {
    return 0;
  } else{
    return 1;
  }
}

Answer 11

The objectsAreSame function mentioned in @JasonBunting's answer works fine for me. However, there's a little problem: If x[propertyName] and y[propertyName] are objects ( typeof x[propertyName] == 'object' ), you'll need to call the function recursively in order to compare them.

Answer 12

I am sharing my compare function implementation as it might be helpful for others:

 /* null AND null // true undefined AND undefined // true null AND undefined // false [] AND [] // true [1, 2, 'test'] AND ['test', 2, 1] // true [1, 2, 'test'] AND ['test', 2, 3] // false [undefined, 2, 'test'] AND ['test', 2, 1] // false [undefined, 2, 'test'] AND ['test', 2, undefined] // true [[1, 2], 'test'] AND ['test', [2, 1]] // true [1, 'test'] AND ['test', [2, 1]] // false [[2, 1], 'test'] AND ['test', [2, 1]] // true [[2, 1], 'test'] AND ['test', [2, 3]] // false [[[3, 4], 2], 'test'] AND ['test', [2, [3, 4]]] // true [[[3, 4], 2], 'test'] AND ['test', [2, [5, 4]]] // false [{x: 1, y: 2}, 'test'] AND ['test', {x: 1, y: 2}] // true 1 AND 1 // true {test: 1} AND ['test', 2, 1] // false {test: 1} AND {test: 1} // true {test: 1} AND {test: 2} // false {test: [1, 2]} AND {test: [1, 2]} // true {test: [1, 2]} AND {test: [1]} // false {test: [1, 2], x: 1} AND {test: [1, 2], x: 2} // false {test: [1, { z: 5 }], x: 1} AND {x: 1, test: [1, { z: 5}]} // true {test: [1, { z: 5 }], x: 1} AND {x: 1, test: [1, { z: 6}]} // false */ function is_equal(x, y) { const arr1 = x, arr2 = y, is_objects_equal = function (obj_x, obj_y) { if (!( typeof obj_x === 'object' && Object.keys(obj_x).length > 0 )) return obj_x === obj_y; return Object.keys(obj_x).length === Object.keys(obj_y).length && Object.keys(obj_x).every(p => is_objects_equal(obj_x[p], obj_y[p])); } ; if (!( Array.isArray(arr1) && Array.isArray(arr2) )) return ( arr1 && typeof arr1 === 'object' && arr2 && typeof arr2 === 'object' ) ? is_objects_equal(arr1, arr2) : arr1 === arr2; if (arr1.length !== arr2.length) return false; for (const idx_1 of arr1.keys()) for (const idx_2 of arr2.keys()) if ( ( Array.isArray(arr1[idx_1]) && this.is_equal(arr1[idx_1], arr2[idx_2]) ) || is_objects_equal(arr1[idx_1], arr2[idx_2]) ) { arr2.splice(idx_2, 1); break; } return !arr2.length; }

Answer 13

using _.some from lodash: https://lodash.com/docs/4.17.11#some

const array1AndArray2NotEqual = 
          _.some(array1, (a1, idx) => a1.key1 !== array2[idx].key1 
                                     || a1.key2 !== array2[idx].key2 
                                     || a1.key3 !== array2[idx].key3);

Answer 14

comparing with json is pretty bad. try this package to compare nested arrays and get the difference.

https://www.npmjs.com/package/deep-object-diff

Answer 15

There`s my solution. It will compare arrays which also have objects and arrays. Elements can be stay in any positions. Example:

const array1 = [{a: 1}, {b: 2}, { c: 0, d: { e: 1, f: 2, } }, [1,2,3,54]];
const array2 = [{a: 1}, {b: 2}, { c: 0, d: { e: 1, f: 2, } }, [1,2,3,54]];

const arraysCompare = (a1, a2) => {
  if (a1.length !== a2.length) return false;
  const objectIteration = (object) => {
    const result = [];
    const objectReduce = (obj) => {
      for (let i in obj) {
        if (typeof obj[i] !== 'object') {
          result.push(`${i}${obj[i]}`);
        } else {
          objectReduce(obj[i]);
        }
      }
    };
    objectReduce(object);
    return result;
  };
  const reduceArray1 = a1.map(item => {
    if (typeof item !== 'object') return item;
    return objectIteration(item).join('');
  });
  const reduceArray2 = a2.map(item => {
    if (typeof item !== 'object') return item;
    return objectIteration(item).join('');
  });
  const compare =  reduceArray1.map(item => reduceArray2.includes(item));
  return compare.reduce((acc, item) => acc + Number(item)) === a1.length;
};

console.log(arraysCompare(array1, array2));

Answer 16

not sure about the performance ... will have to test on big objects .. however, this works great for me.. the advantage it has compared to the other solutions is, the objects/array do not have to be in the same order ....

it practically takes the first object in the first array, and scans the second array for every objects .. if it's a match, it will proceed to another

there is absolutely a way for optimization but it's working :)

thx to @ttulka I got inspired by his work ... just worked on it a little bit

const objectsEqual = (o1, o2) => {
  let match = false
    if(typeof o1 === 'object' && Object.keys(o1).length > 0) {
     match = (Object.keys(o1).length === Object.keys(o2).length && Object.keys(o1).every(p => objectsEqual(o1[p], o2[p])))
    }else {
     match = (o1 === o2)
    }
    return match
}

const arraysEqual = (a1, a2) => {
  let finalMatch = []
  let itemFound = []
  
  if(a1.length === a2.length) {
    finalMatch = []
    a1.forEach( i1 => {
      itemFound = []
      a2.forEach( i2 => { 
        itemFound.push(objectsEqual(i1, i2)) 
      })
        finalMatch.push(itemFound.some( i => i === true))  
    }) 
  } 
  return finalMatch.every(i => i === true)
}

const ar1 = [
  { id: 1, name: "Johnny", data: { body: "Some text"}},
  { id: 2, name: "Jimmy"}
]
const ar2 = [
  {name: "Jimmy", id: 2},
  {name: "Johnny", data: { body: "Some text"}, id: 1}
]


console.log("Match:",arraysEqual(ar1, ar2))

jsfiddle: https://jsfiddle.net/x1pubs6q/

or just use lodash :))))

const _ = require('lodash')

const isArrayEqual = (x, y) => {
  return _.isEmpty(_.xorWith(x, y, _.isEqual));
};

Answer 17

This is work for me to compare two array of objects without taking into consideration the order of the items

 const collection1 = [ { id: "1", name: "item 1", subtitle: "This is a subtitle", parentId: "1" }, { id: "2", name: "item 2", parentId: "1" }, { id: "3", name: "item 3", parentId: "1" }, ] const collection2 = [ { id: "3", name: "item 3", parentId: "1" }, { id: "2", name: "item 2", parentId: "1" }, { id: "1", name: "item 1", subtitle: "This is a subtitle", parentId: "1" }, ] const contains = (arr, obj) => { let i = arr.length; while (i--) { if (JSON.stringify(arr[i]) === JSON.stringify(obj)) { return true; } } return false; } const isEqual = (obj1, obj2) => { let n = 0 if (obj1.length !== obj2.length) { return false; } for (let i = 0; i < obj1.length; i++) { if (contains(obj2, obj1[i])) { n++ } } return n === obj1.length } console.log(isEqual(collection1,collection2))

if you take into consideration the order of the items user build n function in lodash isEqual

Answer 18

If you stringify them...

type AB = {
  nome: string;
}

const a: AB[] = [{ nome: 'Célio' }];
const b: AB[] = [{ nome: 'Célio' }];

console.log(a === b); // false
console.log(JSON.stringify(a) === JSON.stringify(b)); // true