CODEWITHSUNDEEP
javascript
Alwaysblue
Alwaysblue

Reputation: 11900

How to add index value in filter

Consider I have an array-object which looks like this

const options = [{ label: "" }, { label: "123" }]

Now, I want to filter it and remove object which have label value equal to "" and then add order property equivalent to index to those object in an array having some value for label

I am able to do with combination of lodash filter and map but I was thinking if I could do it in a better way (probably using just filter?)

    const options = _.filter(options, "label").map(
      (option, position) => {
        return {
          ...option,
          order: position
        }
      }
    )

Upvotes: 0

Views: 893

Answers (3)

PoryaGrand
PoryaGrand

Reputation: 91

as i understand , you can use the pure js filter :

const options = [{
  label: ""
}, {
  label: "123"
}]
var index = 0;
const res = options.filter((e, i) => {
  e = Object.assign(e,{});
  if (e.label) {
    e.order = index++;
    return e;
  }
})
console.log(res)

Edit: you can also use map and new array to call one function and remain your source pure:

const options = [{
  label: ""
}, {
  label: "123"
}]


var newArr = [];
options.map((e,r)=>{
    if(e.label){
        newArr.push({...e,order:newArr.length});
    }
})

console.log(options)
console.log(newArr)

Upvotes: 0

Devchris
Devchris

Reputation: 412

Another pure JS solution could be:

const options = [{ label: "" }, { label: "123" }];
const modified = options.filter((el) => el.label.length).map((option, i) => ({ ...option, order: i }));
console.log(modified);

Upvotes: 0

Nick Parsons
Nick Parsons

Reputation: 50884

I personally think that what you have now is fine as its quite readable. One different idea could be to use _.flatMap() instead, which will only require one iteration of your options array. If the label is present in an object then you can return the modified object. If the label isn't present then you can return an empty array. As you're flattening into the resulting array for every value you return, the empty array won't be included in the resulting array.

const options = [{ label: "" }, { label: "123" }];
const res = _.flatMap(options, (o, order) => o.label ? {...o, order} : []);
console.log(res);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

Note: You can also use the vanilla version of .flatMap(), so you don't need to use lodash unless you need good browser support or are using it for other code.

Upvotes: 2

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