How to add index to nested array with value 0 or 1 depending on array length

Question

I'm wondering, how to do task like this: I have some array:

var x = [
            {
                "place": 1,
                "name": 'Steve',
            },
            {
                "place": 4,
                "name": 'Ann',
            },
            {
                "place": 9,
                "name": 'John',
            },
        ];

Now i would like to add new value, that will keep index number, to have the result as:

var x = [
            {
                'index':0,
                "place": 1,
                "name": 'Steve',
            },
            {
                'index':1,
                "place": 4,
                "name": 'Ann',
            },
            {
                'index':2,
                "place": 9,
                "name": 'John',
            },
        ];

I've tried this, but seems it's bad solution and not working:

for (var i = 0; i < x.length; i++) {
            arr.push(x['index'],i);
        }

Thanks for help with this, and i don't want to be greddy, but if would be also possible to help with the following it would be extra: Is it possible to have "index" values as 0 or 1, so if for example i have 5 items in array, is there any way to do check in the loop using modulo operaror and assign index value as 0,1,0,1,0? Best regards.

var x = [
            {
                'index':0,
                "place": 1,
                "name": 'Steve',
            },
            {
                'index':1,
                "place": 4,
                "name": 'Ann',
            },
            {
                'index':0,
                "place": 9,
                "name": 'John',
            },
            {
                'index':1,
                "place": 9,
                "name": 'John',
            },
            {
                'index':0,
                "place": 9,
                "name": 'John',
            },
        ];

You can map the array and assign the index: x = x.map((item, index) => Object.assign(item, { index: index % 2 })); jsfiddle.net/k3ghxzeu/1 — briosheje
– briosheje, Commented Oct 13, 2018 at 9:11
do you need the modulo value for display? if so, you could use CSS with nth-child or nth-of-type. — Nina Scholz
– Nina Scholz, Commented Oct 13, 2018 at 9:13
Indeed, it really sounds like you need to use it for display purposes. If so, you don't need to track the indexin this way, as Nina mentioned above — briosheje
– briosheje, Commented Oct 13, 2018 at 9:14

Mohammad Usman · Accepted Answer · 2018-10-13 09:11:54Z

3

You can use .forEach() and modulus operator like this:

var x = [
  {"place": 1, "name": 'Steve'},
  {"place": 4, "name": 'Ann'},
  {"place": 9, "name": 'John'}
];

x.forEach((o, i) => (o.index = i % 2));

console.log(x);

answered Oct 13, 2018 at 9:11

Mohammad Usman

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Comments

Nick · Accepted Answer · 2018-10-13 09:10:35Z

2

You can just loop through the array and add an index value to each object. They can be consecutive or alternate as shown below:

var x = [ { "place": 1, "name": 'Steve' },
          { "place": 4, "name": 'Ann' },
          { "place": 9, "name": 'John' }
        ];
        
for (let i = 0; i < x.length; i++) {
    x[i].index = i;
}
    
console.log(x);
    
for (let i = 0; i < x.length; i++) {
    x[i].index = i % 2;
}
    
console.log(x);

answered Oct 13, 2018 at 9:10

Nick

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1 Comment

Marek Brzeziński Over a year ago

Thank You to Best community in the World. I have so many solutions ....

kiks73 · Accepted Answer · 2018-10-13 09:13:28Z

2

You only need to specify the new attribute for every object in the array:

for (var i = 0; i < x.length; i++) {
        x['index']=i;    
}

If you would like to alternate 0 and 1 as index values, you should use the mod operator and check if the value equals to 0:

for (var i = 0; i < x.length; i++) {
        x['index']=(i % 2 == 0);    
}

answered Oct 13, 2018 at 9:13

kiks73

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Comments

Talg123 · Accepted Answer · 2018-10-13 09:12:46Z

0

first of all you array of objects so u need to run over the array and add each object new "index" property.

x.forEach(function(obj, index){
   obj['Index'] = index;
})

now for if u want 0-1-0-1...

id do smth like htis:

var count = 0;

    x.forEach(function(obj){
      if(count==0){
        obj['Index'] = --count;
      }else{
       obj['Index'] = ++count;
      }
    })

answered Oct 13, 2018 at 9:12

Talg123

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Comments

trk · Accepted Answer · 2018-10-13 09:15:15Z

0

you could say:

x.forEach(function(val, index) {
    //depending on the index you need
    val.index = index // or = index % 2 
})

And, x will have that additional key index with values you need. Let me know if that does not help.

answered Oct 13, 2018 at 9:15

trk

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