how do I check if an item is already in array before adding it to array using Angular?

Question

I want to check if there is an item inside of the array with the same 'datum'. If that is the case I want the program to do nothing, but if that's not the case I want it to add it to my array.

I already have the following code. this just gets the data from input fields in the html, and places the data inside the array.

I only need to check if there's already an item inside with the same 'datum', but I have no idea how to get this done.

store(newValue:number, newDatum, newAanwezig, newComment){
    let billable = new BillableHours();
    billable.datum = newDatum;
    billable.hours = +newValue;
    billable.aanwezig = newAanwezig;
    billable.comment = newComment;

    if(billable.aanwezig == "Aanwezig" && billable.hours !== null && billable.datum !== null) {
      this.urenRegistratie.push(billable);
    }

  }

What about tu use Set: let set = new Set(); on urenRegistratie object? — Milaci
– Milaci, Commented Nov 20, 2019 at 13:14

Artem Krasniuk · Accepted Answer · 2019-11-20 13:13:51Z

2

if (urenRegistratie.some(e => e.datum === newDatum)) {
/* contains the element we're looking for */
}

answered Nov 20, 2019 at 13:13

Artem Krasniuk

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Chris Bendel · Accepted Answer · 2019-11-20 13:16:59Z

1

// Find in your array if there is an item with that datum already. 
const existingDatum = this.urenRegistratie.find(billable => {
  return billable.datum === newDatum;
});

// If you don't have an existing item with the same  datum, then you can create and add it to the array
if (!existingDatum) {
    let billable = new BillableHours();
    billable.datum = newDatum;
    billable.hours = +newValue;
    billable.aanwezig = newAanwezig;
    billable.comment = newComment;

    if(billable.aanwezig == "Aanwezig" && billable.hours !== null && billable.datum !== null) {
      this.urenRegistratie.push(billable);
    }
}

1 Comment

Chris Bendel Over a year ago

developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… In the future: Say you wanted to modify or update the existing object that already has datum with the new data. You could use map to return a new array with the modified item inside the callback

Avi · Accepted Answer · 2019-11-20 13:24:33Z

you can use 'find' or 'findIndex' as follow:

with 'findIndex':

store(newValue:number, newDatum, newAanwezig, newComment){
    let billable = new BillableHours();
    billable.datum = newDatum;
    billable.hours = +newValue;
    billable.aanwezig = newAanwezig;
    billable.comment = newComment;

    if(billable.aanwezig == "Aanwezig" && billable.hours !== null && billable.datum !== null && this.urenRegistratie.findIndex(f=>f.datum ==billable.datum)>-1) {
      this.urenRegistratie.push(billable);
    }

  }

or 'find'

store(newValue:number, newDatum, newAanwezig, newComment){
    let billable = new BillableHours();
    billable.datum = newDatum;
    billable.hours = +newValue;
    billable.aanwezig = newAanwezig;
    billable.comment = newComment;

    if(billable.aanwezig == "Aanwezig" && billable.hours !== null && billable.datum !== null && !this.urenRegistratie.find(f=>f.datum ==billable.datum)) {
      this.urenRegistratie.push(billable);
    }

  }

Good Luck!!!!

AyushKatiyar · Accepted Answer · 2019-11-20 13:21:04Z

0

Try using:

let billable = new BillableHours();
    billable.datum = newDatum;
    billable.hours = +newValue;
    billable.aanwezig = newAanwezig;
    billable.comment = newComment;
var flag = false;
this.urenRegistratie.forEach(elem => {
    if(elem.datum === newDatum){
      flag = true;
    }
});
if(billable.aanwezig == "Aanwezig" && billable.hours !== null && billable.datum !== null) {
if(!flag){
this.urenRegistratie.push(billable);
}
}

answered Nov 20, 2019 at 13:21

AyushKatiyar

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Comments

Adrita Sharma · Accepted Answer · 2019-11-20 13:26:14Z

0

You can use some() to do it.

Try like this:

Working Demo

let billable = { aanwezig: "Aanwezig", hours: 12 }
if (!this.urenRegistratie.some(x => x.aanwezig == billable.aanwezig && x.hours == billable.hours)) {
  this.urenRegistratie.push(billable);
}

edited Nov 20, 2019 at 13:26

answered Nov 20, 2019 at 13:14

Adrita Sharma

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1 Comment

lealceldeiro Over a year ago

Since it's Angular (typescript), it's a good practice to do strict check: index === -1.

Always Learning · Accepted Answer · 2019-11-20 17:49:53Z

0

You can use the Array.prototype.find() function to see if there is already an entry with the same datum value. If not found, it will return undefined and if found you get the array element that matched. The code would look like this:

let element = this.urenRegistratie.find(e => e.datum === newDatum);
if(element) {
 // Found, update it 
}
else {
 // Not found insert new 
 this.urenRegistratie.push(new {})
}

See Array.prototype.find documentation for full details.

edited Nov 20, 2019 at 17:49

Always Learning

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answered Nov 20, 2019 at 13:22

Dipak Telangre

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