如何在UnderscoreJS或angularJS中获得数组的差异

Question

I have two array of objects:

1) [{id:1}{id:2}{id:3}{id:4}{id:5}]

2) [{id:1}{id:2}{id:3}]

is there any in build function in UnderscoreJS or AngularJS which will give me the output as :

[{id:4}{id:5}]

I tried using the _.difference and _.without but this is not working as they work on simple arrays not on array of objects

Thanks in advance.

Answer 1

function diff(a, b) {
  return _.filter(a, function(val) {
    return !_.findWhere(b, val);
  });
}

diff[{id:1}, {id:2}, {id:3}, {id:4}, {id:5}], [{id:1}, {id:2}, {id:3}]); // [{id:4}, {id:5}]

this solution is specific to this data structure and will not work for any array of objects.

Answer 2

I have a stupid way, but it seems to explain the problem.

//arr1.length >= arr2.length
function diff(arr1,arr2){
    var array1 = new Array();
    var array2 = new Array();
    array1 = array1.concat(arr1);
    array2 = array2.concat(arr2);
    for (var i = array1.length - 1; i >= 0; i--) {
        //instead "id" or other
        var idVal = array1[i].id;
        for (var j = array2.length - 1; j >= 0; j--) {
            if(idVal == array2[j].id) {
                //delete the object in array1 and array2
                array1.del(i);
                array2.del(j);
            };
        };
    };
    return array1.concat(array2);
}

Array.prototype.del = function ( dx ) {
    if (isNaN(dx) || dx > this.length) {
        return false;
    }
    for (var i = 0, n = 0; i < this.length; i++) {
        if (this[i] != this[dx]) {
            this[n++] = this[i]
        }
    }
    this.length -= 1
}

Array.prototype.unique = function () {
    var r = new Array();
    label:for(var i = 0, n = this.length; i < n; i++) {
        for(var x = 0, y = r.length; x < y; x++) {
            if(r[x].id == this[i].id) {
                continue label;
            }
        }
        r[r.length] = this[i];
    }
    return r;
}

var array1 = [{id:"1"},{id:"2"},{id:"3"},{id:"4"},{id:"12"},{id:"15"},{id:"15"}].unique();
var array2 = [{id:"1"},{id:"2"},{id:"03"},{id:"4"},{id:"5"},{id:"5"},{id:"5"},{id:"5"},{id:"5"}].unique();
var resultArray = array1.length >= array2.length 
                  ? diff(array1,array2) : diff(array2,array1);
console.log(resultArray);
//[ { id: '3' },{ id: '12' },{ id: '15' },{ id: '03' },{ id: '5' } ]