Removing elements from array after pulling data from firebase

Question

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:

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 ?

felixmosh · Accepted Answer · 2017-12-30 16:33:20Z

1

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);

answered Dec 30, 2017 at 16:33

felixmosh

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MynockSpit · Accepted Answer · 2017-12-30 16:40:13Z

0

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'
})

answered Dec 30, 2017 at 16:40

MynockSpit

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Raju · Accepted Answer · 2017-12-30 17:20:13Z

0

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"}

answered Dec 30, 2017 at 17:20

Raju

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