push a array object into another array object if the value not exists

Question

Need to push the array object(arr1) valeus into another array object(arr2) if the value not exist. The existing values will not push into another array.

var arr1 = [{
    name: 'fred'
}, {
    name: 'bill'
}, {
    name: 'ted'
}, {
    name: 'james'
}];

var arr2 = [{
    name: 'spil'
}, {
    name: 'fred'
}, {
    name: 'bill'
},{
    name: 'paul'
}, {
    name: 'stone'
}];

function add(name) {
    var found = arr1.some(function (el) {
      return el.name === name;
    });
    if (!found) {
        arr1.push(arr2);
    }
    return arr2;
}

Fiddle

Check [this.](http://stackoverflow.com/questions/1584370/how-to-merge-two-arrays-in-javascript-and-de-duplicate-items?answertab=active#tab-top) LiraNuna's answer will help you. — pkovzz, Jun 28 '16 at 06:22
You are talking about pushing values into `arr2`, but your code does the opposite (or sort of tries to). Given that your `add()` function seems to take a string as input, what should happen (a) if the value is currently in neither array? (b) If it is currently in only `arr1`? (c) If it is currently in only `arr2`? (d) If it is already in both arrays? — nnnnnn, Jun 28 '16 at 06:28

score 6 · Accepted Answer · edited Mar 26 '22 at 20:07

You could use a hash table for look up, if the name property is already in arr1. If not push the actual item to arr1.

var arr1 = [{ name: 'fred' }, { name: 'bill' }, { name: 'ted' }, { name: 'james' }],
    arr2 = [{ name: 'toString' }, { name: 'spil' }, { name: 'fred' }, { name: 'bill' }, { name: 'paul' }, { name: 'stone' }],
    hash = Object.create(null);

arr1.forEach(function (a) {
    hash[a.name] = true;
});
arr2.forEach(function (a) {
    hash[a.name] || arr1.push(a);
});

console.log(arr1);

PS

Just to make clear, why Object.create(null), a really empty object as hash and not {}, an empty object. Pay attention to the item { name: 'toString' }. In the first part, the item gets inserted, in the second not, because hash has a property with the name toString.

var arr1 = [{ name: 'fred' }, { name: 'bill' }, { name: 'ted' }, { name: 'james' }],
    arr2 = [{ name: 'toString' }, { name: 'spil' }, { name: 'fred' }, { name: 'bill' }, { name: 'paul' }, { name: 'stone' }],
    hash = {}; // now an object

arr1.forEach(function (a) {
    hash[a.name] = true;
});
arr2.forEach(function (a) {
    hash[a.name] || arr1.push(a);
});

console.log(arr1);

score 1 · Answer 2 · answered Jun 28 '16 at 06:27

If you're only appending a single variable, then push() works just fine. If you need to append another array, use concat(): var ar1 = [1, 2, 3]; var ar2 = [4, 5, 6];

var ar3 = ar1.concat(ar2);

alert(ar1);
alert(ar2);
alert(ar3);

Will spit out:

"1,2,3"
"4,5,6"
"1,2,3,4,5,6"

The concat does not affect ar1 and ar2 unless reassigned, for example:

ar1 = ar1.concat(ar2);
alert(ar1);

Will display:

"1,2,3,4,5,6"

score 1 · Answer 3 · answered Jun 28 '16 at 06:29

1

Hi check this u can push the first array to other array later can use the underscore unique to return only the unique objects

   var arr1 = [{
    name: 'fred'
}, {
    name: 'bill'
}, {
    name: 'ted'
}, {
    name: 'james'
}];

var arr2 = [{
    name: 'spil'
}, {
    name: 'fred'
}, {
    name: 'bill'
}, {
    name: 'paul'
}, {
    name: 'stone'
}];

arr1.push(arr2);
arr1 = _.uniq(arr1, false, function(p) {
    return p.name;
});

answered Jun 28 '16 at 06:29

Gayathri Mohan

2,924
4
19
25

And for the JS beginner who doesn't know what Underscore is? (Also, you're pushing the entire `arr2` array as a single element of `arr1` - I know the OP's code did this, but I don't think it's what they want.) – nnnnnn Jun 28 '16 at 06:31
ha u started again @nnnnnn – Gayathri Mohan Jun 28 '16 at 06:31

Jack jdeoel · Answer 4 · 2016-06-28T07:22:39.960

1

Use indexOf for get not exist name.Store first your arr1 name as a array !!!

var hasName = arr1.map(function(obj) { return obj.name; });
arr2.filter(function(v,i) { if(hasName.indexOf(v.name) == -1) arr1.push(v); });      
console.log(arr1);

edited Jun 28 '16 at 07:22

answered Jun 28 '16 at 07:13

Jack jdeoel

4,554
5
26
52

Grgur · Answer 5 · 2016-06-28T07:29:51.763

If you have the luxury of using ECMAScript 6 then you can create this lovely block

var arr1 = [{
    name: 'fred'
}, {
    name: 'bill'
}, {
    name: 'ted'
}, {
    name: 'james'
}];

var arr2 = [{
    name: 'spil'
}, {
    name: 'fred'
}, {
    name: 'bill'
},{
    name: 'paul'
}, {
    name: 'stone'
}];

arr2.forEach(arr2Item => arr1.find(({ name }) => name === arr2Item.name) || arr1.push(arr2Item));

console.log(arr1);

Given that there's plenty of recursion, you may want to store your data in a different format so you can compare more easily. You could use object hash or ES6 Map to make your life easier. Also to save a few cycles

push a array object into another array object if the value not exists

5 Answers5

Linked