comparing two arrays before adding an item from one array to another in JavaScript [closed]

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I have two arrays.

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"];
var addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];

I would like to check if the first item in "addFrom" array is already in "addTo" array.

If the "addTo" array does not have the first item in "addFrom" array, I would like to push this item to "addTo" array.

However, if the first item in the "addFrom" array is already in the "addTo" array, I would like to move on to the second item in the "addFrom" array and do the same thing until I find the item in the "addFrom" array that is not in the "addTo" array, which will then be pushed to the "addTo" array. and I want to add only one item to the "addTo" array.

As a result, I want the "addTo" array to look like this:

var addTo = ["pear", "tangerine", "grape", "orange", "blueberry", "banana"];

How can I do this in JavaScript?

please add the wanted result.

Nina Scholz
– Nina Scholz

2016-04-14 20:34:02 +00:00
Commented Apr 14, 2016 at 20:34 — Nina Scholz
– Nina Scholz, Commented Apr 14, 2016 at 20:34

Nina Scholz · Accepted Answer · 2016-04-14 20:40:42Z

2

You could use Array#some() and stop the iteration if one item is not in the addTo array.

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"],
    addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];

addFrom.some(function (a) {
    if (!~addTo.indexOf(a)) {
        addTo.push(a);
        return true;
    }
});

document.write('<pre> ' + JSON.stringify(addTo, 0, 4) + '</pre>');

answered Apr 14, 2016 at 20:40

Nina Scholz

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Andy · Accepted Answer · 2016-04-14 20:47:08Z

1

A simple loop seems the best approach here (I've used while).

var i = -1, len = addFrom.length;
while (++i < len) {
  if (addTo.indexOf(addFrom[i]) === -1) {
    addTo.push(addFrom[i]);
    break;
  }
}

DEMO

answered Apr 14, 2016 at 20:47

Andy

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Comments

jDo · Accepted Answer · 2016-04-14 21:07:43Z

1

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"];
var addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];

for(var i = 0; i < addFrom.length; i++){   
    if(addTo.indexOf(addFrom[i]) === -1 ){
        addTo.push(addFrom[i]); 
        break; 
    }    
}

edited Apr 14, 2016 at 21:07

answered Apr 14, 2016 at 20:55

jDo

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Comments

Maxi Schvindt · Accepted Answer · 2016-04-14 20:45:41Z

0

https://jsfiddle.net/povvx8hg/

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"];
var addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];

for (i = 0; i < addFrom.length; i++) {
    if(addTo.indexOf(addFrom[i]) != -1) {
    console.log("Exist");
  } else {
    addTo.push(addFrom[i]);
  }
}

console.log(addTo);

answered Apr 14, 2016 at 20:45

Maxi Schvindt

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2 Comments

Maxi Schvindt Over a year ago

Check console browser!

yezzz Over a year ago

you forgot to break out of loop after first push

ansanes · Accepted Answer · 2016-04-14 20:47:44Z

0

Easy peasy

for (index = 0; index < addFrom.length; ++index) {
  if (addTo.indexOf(addFrom[index]) === -1){
      addTo.push(addFrom[index]);
      break;
  }
}

answered Apr 14, 2016 at 20:47

ansanes

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1 Comment

Andy Over a year ago

Make sure you var your loop variable(s).

Mahmoud Fakhry · Accepted Answer · 2019-09-02 13:30:58Z

-1

You can use forEach

var addFrom = ["orange", "banana", "watermelon", "lemon", "peach"];
var addTo = ["pear", "tangerine", "grape", "orange", "blueberry"];
var inserted = false;

    addFrom.forEach(function(v,i){
        if(inserted)
           return;

        if(addTo.indexOf(v)<0)
        {
            addTo.push(v);
            inserted = true;
        }
    })

edited Sep 2, 2019 at 13:30

answered Apr 14, 2016 at 20:39

Mahmoud Fakhry

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2 Comments

Andy Over a year ago

From the question: "I want to add only one item to the "addTo" array". This code will push all missing elements from addFrom

Mahmoud Fakhry Over a year ago

sorry, my fault I edited the answer

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