如何根据对对象的了解，从数组中查找和删除对象？

Question

For the following:

var arr = [{ "packageId": "11", "machineId": "1", "operationType": "Download" }, { "packageId": "12", "machineId": "1", "operationType": "Download" }, { "packageId": "14", "machineId": "1", "operationType": "Download" }];
var index = arr.indexOf({ "packageId": "12", "machineId": "1", "operationType": "Download" });
console.log("index: " + index);
arr.splice(index, 1);

I always get -1 as a result. Why is that?

I need to be able to remove an object from an array.

Answer 1

[Note in reference to the original wording of your question: There is no JSON in your question actually; JSON refers to object notation. What you have inside your array and your indexOf() call are object literals, represented by {} with optional properties inside.]

COMPARING OBJECTS

The problem is that the object literal you create inside your indexOf() call is a new object unto itself and therefore not equal to anything inside the array arr . Instead, you have to loop through all the properties in each object and check their equivalence. I wrote this function quickly now and you can test it in the JSFiddle link at the bottom of this answer.

function compareObjs(obj1, obj2) {
    var k,
        rtn = true; // assume objects are similar, and then attempts to falsify
    for (k in obj1) {
        if (obj1.hasOwnProperty(k) && obj2.hasOwnProperty(k)) { // check property belongs to both obj1 and obj2
            if (typeof obj1[k] === 'Object') {
                compareObjs(obj1, obj2); // recursive call, to compare two objects within the object
            } else {
                rtn = (obj1[k] === obj2[k]) ? rtn : false; // check value of property is equivalent; if not set the return value to false
            }
        } else {
            rtn = false;
        }
    }
}

You feed it two objects, so in your question that would be:

compareObjs(arr[1], { "packageId": "12", "machineId": "1", "operationType": "Download" });

This should return true. If the two objects aren't equivalent then it will return false.

FINDING AN ARRAY ELEMENT

I'm guessing you would want to use this to check the position of a particular package in the array, in which case you would probably need to loop through your array checking each object in it for equivalence, like so:

var i = 0, // Declare the variables upfront
    l = arr.length, // including the length of the array
    r = -1;  // and where you want your result, which will automatically be -1 until a match is found.
for (i; i < l; i += 1) {
    r = (compareObjs(arr[i], { "packageId": "12", "machineId": "1", "operationType": "Download" }) && r === -1) ? i : r;
}

Here r should give you the first position in which an equivalent object is found.

REMOVING THE RELEVANT ARRAY ELEMENT

You can then remove the object from the array with reference to r , using the splice() method like so:

arr.splice(r, 1);

You might want to drop this code into a function too but I don't know the structure of the rest of your programme so will leave you to ponder that!

JSFiddle here . (You will need to open the browser console to view the results.)

Answer 2

The {} object literal you are creating is actually a different object than the object in arr , so they cannot be compared directly and indexOf will fail. You have to use good old fashioned iteration:

arr.filter(function (elem) {
    return elem.packageId != 12
        || elem.machineId != 1
        || elem.operationType != 'Download';
});

You can of course also compare to an object if you need.

var compareTo = {'packageId': '12'};
arr.filter(function (elem) {
    var matches = 0, elements = 0;
    for (var x in compareTo) {
        elements++;
        if (compareTo.hasOwnProperty(x) && elem.hasOwnProperty(x)
            && elem (x) == compareTo(x)
        ) {
            matches++;
        }
    }
    return matches == elements;
});

Answer 3

I suggest you another possible solution.

If you can modify your data structure, use an Object in order to store your data, an shape it as an associative array:

var assocArr = new Object();
assocArr["11"] = {"packageId": "11", "machineId": "1", "operationType": "Download"};
assocArr["12"] = { "packageId": "12", "machineId": "1", "operationType": "Download" };
assocArr["14"] = { "packageId": "14", "machineId": "1", "operationType": "Download" };

delete assocArr["11"];

Advantages:

• direct data access
• trivial insert and deletion

You could also arrange a class to manage your data:

var AssocArray = function(){
  var collection = new Object();

  this.add = function(id, o){
    collection[id] = o;
  }

  this.remove = function(id){
    delete collection[id];
  }

  this.getById = function(id){
    return collection[id];
  }

  this.get = function(){
    return collection;
  }
}

var myAssoc = new AssocArray();
myAssoc.add("11",{"packageId": "11", "machineId": "1", "operationType": "Download"});
myAssoc.add("12",{ "packageId": "12", "machineId": "1", "operationType": "Download"});
myAssoc.add("14",{ "packageId": "14", "machineId": "1", "operationType": "Download"});

if(myAssoc.getById("10")) myAssoc.remove("10");
if(myAssoc.getById("14")) myAssoc.remove("14");

console.log(myAssoc.get());