CODEWITHSUNDEEP
javascript
Evanss
Evanss

Reputation: 23563

Chain push along with filter, map etc in JavaScript?

I have a function which returns an array which has filter, sort and map. How can I push a new item into the array before its sorted?

When I try the following I get an error saying push isnt a function. 

return (
  myArray
    .filter((item) => {
      return item.value > 2;
    })
    .push(newThiny) // This doesn't work
    .sort((a, b) => {
      if (a.name < b.name)
        return -1;
      if (a.name > b.name)
        return 1;
      return 0;
    })
    .map((item) => {
      return (
        <ChooseAnExercises
          key={item.name}
          name={item.name}
          active={item.active}
          setNumber={this.props.number}
          updateValue={this.props.updateValue}
        />
      )
    })
)

Upvotes: 5

Views: 2548

Answers (3)

SweetWalker
SweetWalker

Reputation: 1

.push() return a length of array. You can wrap your expression with ()

See the Example:

var arr = [ 0, 1, 2, 3, 4];

var arr2 = arr.filter( item => item > 2).push('Some');

console.log(arr2, 'doesnt works. You get the length of array');

(b = arr.filter(item => item > 2)).push('Some');

console.log(b, 'Works Correctly. In Array');

Upvotes: 0

gurvinder372
gurvinder372

Reputation: 68393

.push(newThiny) // This doesn't work

Push returns the length of the array rather than the array itself.

Rather than push try concat

.concat([newThiny])

Upvotes: 5

kind user
kind user

Reputation: 41893

.push(newThiny) will return a number so .sort function will throw an error, since it doesn't work on numbers, only on arrays.

I would suggest you to use .concat instead.

.concat(newThiny).sort({ ... })

Upvotes: 7

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