Explore within another map and analyze the node to spot the differences

Question

Explore within another map and analyze the node to spot the differences

I have some questions about iterating through a JavaScript Object and using array functions in JavaScript. Let's assume I have the following variables:

var json1 = "[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}]";
var json2 = "[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}]";

How can I create a variable containing only the IDs in an array?

var ids1 = json1.ids (resulting in 1,2)
var ids2 = json2.ids (resulting in 1,2,3)

Furthermore, how can I create another variable with only the IDs that are different between the two arrays?

var idsdiff = diff(ids1, ids2) (resulting in 3)

javascript arrays json

Answer 1

Answer №1

var json1 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}],
    json2 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}, {"id":3,"name":"z"}],
    result1 = json1.map(function (a) { return a.id; }),
    result2 = json2.map(function (a) { return a.id; });

var differences = result2.filter(function (item) {
    return result1.indexOf(item) < 0;
});

console.log(result1);
console.log(result2);
console.log(differences);

Note that indexOf, filter, and map may not work in iE versions before iE9.

UPDATE: According to @alexandru-Ionutmihai's comment, filter will fail on arrays like [1,2,4] and [1,2,3]

This revised code seems more accurate:

var json1 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}],
        json2 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}, {"id":3,"name":"z"}],
        result1 = json1.map(function (a) { return a.id; }),
        result2 = json2.map(function (a) { return a.id; });

//as per @alexandru-Ionutmihai this is inaccurate for [1,2,4] and [1,2,3]
/*var differences = result2.filter(function (item) {
    return result1.indexOf(item) < 0;
});*/

//here's a workaround
function findDifferences(a, b) {
  var i,
    la = a.length,
    lb = b.length,
    res = [];
  if (!la)
    return b;
  else if (!lb)
    return a;
  for (i = 0; i < la; i++) {
    if (b.indexOf(a[i]) === -1)
      res.push(a[i]);
  }
  for (i = 0; i < lb; i++) {
    if (a.indexOf(b[i]) === -1) res.push(b[i]);
  }
  return res;
}

var differences = findDifferences(result1, result2),
  testDiff = findDifferences([1, 2, 4], [1, 2, 3]);

console.log(result1);
console.log(result2);
console.log(differences);
console.log(testDiff);

findDifferences credit to @Nomaed's comment on this question's answer.

Answer 2

var json1 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}],
    json2 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}, {"id":3,"name":"z"}],
    result1 = json1.map(function (a) { return a.id; }),
    result2 = json2.map(function (a) { return a.id; });

var differences = result2.filter(function (item) {
    return result1.indexOf(item) < 0;
});

console.log(result1);
console.log(result2);
console.log(differences);

Note that indexOf, filter, and map may not work in iE versions before iE9.

UPDATE: According to @alexandru-Ionutmihai's comment, filter will fail on arrays like [1,2,4] and [1,2,3]

This revised code seems more accurate:

var json1 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}],
        json2 = [{"id":1,"name":"x"}, {"id":2,"name":"y"}, {"id":3,"name":"z"}],
        result1 = json1.map(function (a) { return a.id; }),
        result2 = json2.map(function (a) { return a.id; });

//as per @alexandru-Ionutmihai this is inaccurate for [1,2,4] and [1,2,3]
/*var differences = result2.filter(function (item) {
    return result1.indexOf(item) < 0;
});*/

//here's a workaround
function findDifferences(a, b) {
  var i,
    la = a.length,
    lb = b.length,
    res = [];
  if (!la)
    return b;
  else if (!lb)
    return a;
  for (i = 0; i < la; i++) {
    if (b.indexOf(a[i]) === -1)
      res.push(a[i]);
  }
  for (i = 0; i < lb; i++) {
    if (a.indexOf(b[i]) === -1) res.push(b[i]);
  }
  return res;
}

var differences = findDifferences(result1, result2),
  testDiff = findDifferences([1, 2, 4], [1, 2, 3]);

console.log(result1);
console.log(result2);
console.log(differences);
console.log(testDiff);

findDifferences credit to @Nomaed's comment on this question's answer.

Answer 3

Answer №2

To find the difference between two sets of values, you can utilize a hash table to store the IDs and their occurrences. Then, filter out the IDs with a count that is not zero to get the unique values.

function getId(a) { return a.id; }

var obj1 = JSON.parse('[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}]');
var obj2 = JSON.parse('[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}]');
var ids1 = obj1.map(getId);
var ids2 = obj2.map(getId);
var hash = {};

ids1.forEach(function (a) {
    hash[a] = 1;
});
ids2.forEach(function (a) {
    hash[a] = (hash[a] || 0) - 1;
});

var difference = Object.keys(hash).filter(function (a) { return hash[a]; }).map(Number);
console.log(ids1);
console.log(ids2);
console.log(hash);
console.log(difference);

.as-console-wrapper { max-height: 100% !important; top: 0; }

For a symmetrical difference, you can make use of lodash's _.xor method.

var ids1 = [1, 2],
    ids2 = [1, 2, 3];

console.log(_.xor(ids1, ids2));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

Answer 4

To find the difference between two sets of values, you can utilize a hash table to store the IDs and their occurrences. Then, filter out the IDs with a count that is not zero to get the unique values.

function getId(a) { return a.id; }

var obj1 = JSON.parse('[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}]');
var obj2 = JSON.parse('[{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}]');
var ids1 = obj1.map(getId);
var ids2 = obj2.map(getId);
var hash = {};

ids1.forEach(function (a) {
    hash[a] = 1;
});
ids2.forEach(function (a) {
    hash[a] = (hash[a] || 0) - 1;
});

var difference = Object.keys(hash).filter(function (a) { return hash[a]; }).map(Number);
console.log(ids1);
console.log(ids2);
console.log(hash);
console.log(difference);

.as-console-wrapper { max-height: 100% !important; top: 0; }

For a symmetrical difference, you can make use of lodash's _.xor method.

var ids1 = [1, 2],
    ids2 = [1, 2, 3];

console.log(_.xor(ids1, ids2));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

Answer 5

Answer №3

If you haven't already parsed the JSONs, an additional step is required:

json1 = JSON.parse(json1);

If they have been parsed, please implement this code snippet instead:

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];

// Additional steps if needed
// json1 = JSON.parse(json1);
// json2 = JSON.parse(json2);

function returnID (item) {
    return item.id;
};

json1 = json1.map(returnID);
json2 = json2.map(returnID);

var diff = json2.filter(function (item) {
    return json1.indexOf(item) < 0;
});

console.log(diff);

Answer 6

If you haven't already parsed the JSONs, an additional step is required:

json1 = JSON.parse(json1);

If they have been parsed, please implement this code snippet instead:

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];

// Additional steps if needed
// json1 = JSON.parse(json1);
// json2 = JSON.parse(json2);

function returnID (item) {
    return item.id;
};

json1 = json1.map(returnID);
json2 = json2.map(returnID);

var diff = json2.filter(function (item) {
    return json1.indexOf(item) < 0;
});

console.log(diff);

Answer 7

Answer №4

To compare two sets of JSON data, you can utilize the map method along with the filter method.

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];
var j1=json1.map((x)=>{return x.id});
var j2=json2.map((x)=>{return x.id});
var diff = j2.filter(function(el){
    return j1.indexOf(el)==-1;
}).concat(j1.filter(function(el){
    return j2.indexOf(el)==-1;
}));
console.log(diff);

This code is designed to work effectively when the IDs present in both JSON arrays are different from each other.

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 4, "name":"y"}, {"id": 5, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];
var j1=json1.map((x)=>{return x.id});
var j2=json2.map((x)=>{return x.id});
var diff = j2.filter(function(el){
    return j1.indexOf(el)==-1;
}).concat(j1.filter(function(el){
    return j2.indexOf(el)==-1;
}));
console.log(diff);

Answer 8

To compare two sets of JSON data, you can utilize the map method along with the filter method.

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];
var j1=json1.map((x)=>{return x.id});
var j2=json2.map((x)=>{return x.id});
var diff = j2.filter(function(el){
    return j1.indexOf(el)==-1;
}).concat(j1.filter(function(el){
    return j2.indexOf(el)==-1;
}));
console.log(diff);

This code is designed to work effectively when the IDs present in both JSON arrays are different from each other.

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 4, "name":"y"}, {"id": 5, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];
var j1=json1.map((x)=>{return x.id});
var j2=json2.map((x)=>{return x.id});
var diff = j2.filter(function(el){
    return j1.indexOf(el)==-1;
}).concat(j1.filter(function(el){
    return j2.indexOf(el)==-1;
}));
console.log(diff);

Answer 9

Answer №5

For populating arrays with only the id attributes of each object, you can simply do...

var ids1 = json1.map(x => x.id)
var ids2 = json2.map(x => x.id)

If you are using ES6 or a version transpiler, you have the option to utilize the spread operator to find the variance between the two like so:

var diff = [...ids1.filter(x => !ids2.includes(x)), ...ids2.filter(x => !ids1.includes(x))]

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];

var ids1 = json1.map(x => x.id);
var ids2 = json2.map(x => x.id);

var diff = [...ids1.filter(x => !ids2.includes(x)), ...ids2.filter(x => !ids1.includes(x))];
console.log(diff);

Answer 10

For populating arrays with only the id attributes of each object, you can simply do...

var ids1 = json1.map(x => x.id)
var ids2 = json2.map(x => x.id)

If you are using ES6 or a version transpiler, you have the option to utilize the spread operator to find the variance between the two like so:

var diff = [...ids1.filter(x => !ids2.includes(x)), ...ids2.filter(x => !ids1.includes(x))]

var json1 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}];
var json2 = [{"id": 1, "name":"x"}, {"id": 2, "name":"y"}, {"id": 3, "name":"z"}];

var ids1 = json1.map(x => x.id);
var ids2 = json2.map(x => x.id);

var diff = [...ids1.filter(x => !ids2.includes(x)), ...ids2.filter(x => !ids1.includes(x))];
console.log(diff);

Answer 11

Answer №6

Below are two functions provided for you to achieve your desired results:

Function One (retrieveIds):

var data1 = [{"id": 1, "name":"apple"}, {"id": 2, "name":"banana"}];
var data2 = [{"id": 1, "name":"apple"}, {"id": 2, "name":"banana"}, {"id": 3, "name":"cherry"}];

function retrieveIds (data) {
    return data.map(function (object) {
        return object.id;
    });
}

console.log(retrieveIds(data1));
console.log(retrieveIds(data2));

Function Two (findDifference)

var data1 = [1, 2, 4, 6];
var data2 = [1, 2, 3];

function findDifference (arr1, arr2) {
    return arr1.concat(arr2).filter(function (num, index, array) {
        return array.indexOf(num) === array.lastIndexOf(num);
    });
}

console.log(findDifference(data1, data2));

Answer 12

Below are two functions provided for you to achieve your desired results:

Function One (retrieveIds):

var data1 = [{"id": 1, "name":"apple"}, {"id": 2, "name":"banana"}];
var data2 = [{"id": 1, "name":"apple"}, {"id": 2, "name":"banana"}, {"id": 3, "name":"cherry"}];

function retrieveIds (data) {
    return data.map(function (object) {
        return object.id;
    });
}

console.log(retrieveIds(data1));
console.log(retrieveIds(data2));

Function Two (findDifference)

var data1 = [1, 2, 4, 6];
var data2 = [1, 2, 3];

function findDifference (arr1, arr2) {
    return arr1.concat(arr2).filter(function (num, index, array) {
        return array.indexOf(num) === array.lastIndexOf(num);
    });
}

console.log(findDifference(data1, data2));

Explore within another map and analyze the node to spot the differences

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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