Best way to map a string to an array depending on other array values

Question

Given an array:

var arrOfObj = [{
  name: 'eve',
  col1 : 1,
  col2 : 0,
  col3 : 1
}, {
  name: 'john',
    col1 : 1,
  col2 : 1,
  col3 : 0
}, {
  name: 'jane',
  col1 : 0,
  col2 : 1,
  col3 : 1
}];

I need a field inside the array that has a string of the names of columns col1, col2, col3 if they are 1. Sample outcome is:

var arrOfObj = [{
  name: 'eve',
  col1 : 1,
  col2 : 0,
  col3 : 1,
  account : "col1,col3"
} //etc
}]

I can currently achieve this with

var result = arrOfObj.map(function(o) {
  o.account = ""
  if (o.col1 > 0) {o.account  = o.account + "col1,"} ;
  if (o.col2 > 0) {o.account= o.account + "col2,"} ;
  if (o.col3 > 0) {o.account= o.account + "col3,"} ;
  o.account = o.account.slice(0, -1);
  return o;
})

console.log(result)

but as a novice to JS this feels inefficient. My actual array has a dozen such columns being evaluated.

Edit: finished product with assistance from the accepted answer:

var bool_cols = ["col1","col2","col3"]

data.forEach(x => {
        x.services = Object.keys(x).filter (y => bool_cols.includes(x) && x[y] == 1).join (',');
    })

I like how I can expand the filter criteria indefinitely!

flappix · Accepted Answer · 2020-01-12 19:48:32Z

3

How about

arrOfObj.forEach ( (x) => {
    x.account = Object.keys(x).filter (y => x[y] == 1).join (',');
})

answered Jan 12, 2020 at 19:48

flappix

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3 Comments

DCUFan7 Over a year ago

Could I do that on only certain parts of the array? Col1, 2, and 3 but not Name?

flappix Over a year ago

@DCUFan7 you can add more conditions inside the filter function like filter (y => x[y] == 1 && y.contains("col") )

DCUFan7 Over a year ago

I love this for making use of filter and join. Looking like includes works for me as well on the second filter. Thank you!

Maheer Ali · Accepted Answer · 2020-01-12 19:40:41Z

2

I would loop over the keys of the object. And check if key starts with 'col'

var arrOfObj = [{
  name: 'eve',
  col1 : 1,
  col2 : 0,
  col3 : 1
}, {
  name: 'john',
    col1 : 1,
  col2 : 1,
  col3 : 0
}, {
  name: 'jane',
  col1 : 0,
  col2 : 1,
  col3 : 1
}];

const res = arrOfObj.map(x => {
  let acc = [];
  Object.keys(x).forEach(k => {
    if(k.startsWith('col') && x[k] === 1){
      acc.push(k)
    }
  })
  return {...x, account: acc.join(',')}
});

console.log(res)

answered Jan 12, 2020 at 19:40

Maheer Ali

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Comments

Athanasios Kataras · Accepted Answer · 2020-01-13 16:38:52Z

1

You can use the var Object.keys(object); to get the keynames of the object and then check the values.

var result = arrOfObj.map(function(o) {
  var keys = Object.keys(o);
  var keyArray = [];
  keys.forEach((key) => {
      if (o[key] > 0) { 
        // Declare the account property, only
        // when it's needed. Otherwise, get it out of the foreach
        keyArray.push(key);
      }
  });
  o['account'] = keyArray.join(',');
});

edited Jan 13, 2020 at 16:38

answered Jan 12, 2020 at 19:38

Athanasios Kataras

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4 Comments

Athanasios Kataras Over a year ago

Updated with the comma.

balexandre Over a year ago

@AthanasiosKataras that pattern is just bad code, just push into an array and then join by comma at the end ...

Cooper Buckingham Over a year ago

Why bother setting the account to an empty string before appending the key. Just set it to the key. Also, working the comma separator into the appended string value just causes confusion and makes it more difficult to manage later when inputs change. Using a join instead, solves all that.

Athanasios Kataras Over a year ago

Because += resulted in undefinedcol1.

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