CODEWITHSUNDEEP
javascriptarraysfirebase
Yunus Emre Guney Student
Yunus Emre Guney Student

Reputation: 131

Removing elements from array after pulling data from firebase

I am pulling an object from firebase converting it to an array then doing remove element operation on it but there is some strange behaviour:

this.players = this.db.object('arena/players').valueChanges();
  this.players.subscribe(players =>{
console.log(players);
    this.playersarray= Object.keys(players).map(key => ({ key, value: players[key] }));
    console.log(this.playersarray);
    console.log(this.playersarray.length);

    for(var i =0;i<this.playersarray.length;i++){

        if(this.playersarray[i].value != "waiting"){
          console.log(this.playersarray[i].value+"deleting");
          this.playersarray.splice(i,1);
        }

    }


console.log(this.playersarray);


  });

This is console: enter image description here

I am trying to remove elements which value are not equal to waiting.So in this case im expecting to remove engincan,lifesuxtr and get last console.log as only someotheruser,someuser but lifesuxtr is not removed ??? only engincan removed ?

Upvotes: 0

Views: 425

Answers (3)

Raju
Raju

Reputation: 160

Simple way to remove array element by value.

var playersarray = {
    "name": "John",
    "age": 30,
    "cars": "Ford"
};

for(value in playersarray){
  if(playersarray[value] != "Ford"){
    delete playersarray[value]; //deleting array elements if no 'Ford'

  }
}
console.log(playersarray);

Output: {cars:"Ford"}

Upvotes: 0

MynockSpit
MynockSpit

Reputation: 449

When you remove the items from the array, the index of all following items shift down. Because you're removing an item, your loop skips an item.

// Array starts as:
//   0    1    2    3
// ['a', 'b', 'c', 'd']

// Loop 1: Index 0, item 'a'. Matches test, remove it.

// Array becomes:
//   0    1    2
// ['b', 'c', 'd']

// Loop 2: Index 1, item 'c'. 
// Loop 3: Index 2, item 'd'.

The quickest fix is to change the index by subtracting one from it but that's can get hard to keep track of quickly. I'd recommend using the Array.filter() method.

this.playersarray = this.playersarray.filter(function(player) {
  return player.value != 'waiting'
})

Upvotes: 0

felixmosh
felixmosh

Reputation: 35553

You can use Array.filter operator to iterate over the Array and filter our the relevant results, example:

const arr = [1, 2, 3, 4, 5];

const result = arr.filter((item) => item % 2 === 1);

console.log(result);

Upvotes: 1

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