How to compare values of two objects in Angular

Question

I am pushing row dynamically on add new button click in my form. The new data will be added in oldData array in the form of object.

I want to match all values of newData object with oldData array, if newData object with same values is available in oldData array of objects, Then code will console error else it push the row.

Can anyone please help me to make my function working.

This is not a question of angular itself. The error should show up if one value exists or ALL values are the same? — DonJuwe, Feb 16 '22 at 12:46
Yong Shun has the correct answer, which is "no, not out of the box", do use a library like lodash. Elegantly, he does so by linking to a previous question/answer! — JSmart523, Feb 16 '22 at 13:38

José Polanco · Answer 1 · 2022-02-16T13:59:24.340

0

I do it like this:

private allElementExists(newData: any[], oldData: any[]): boolean {
    for (const item of newData) {
        var verifyItem = oldData.find(x => x.id === item.id);
        if (verifyItem === undefined) {
            return false;
        }
    }
    return true;
}

Here you have a function that compares the two objets as you putted in your question

Here is an example in stackblitz using this function

https://stackblitz.com/edit/angular-xscnkf?file=src%2Fapp%2Fapp.component.html

edited Feb 16 '22 at 13:59

answered Feb 16 '22 at 12:58

José Polanco

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4
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@JosePolance, I wanted to check if all values of newdata are exist in oldData object then only error will come – Shubham pandey Feb 16 '22 at 13:01
@JosePolance, i wanted to check if more than one object with same value is available then it throw error – Shubham pandey Feb 16 '22 at 13:13
@Shubham pandey I've Updated the response. – José Polanco Feb 16 '22 at 13:45
@JosePolnaco,Its working fine, but i want if same data available more than one, than only it will throw error, but in your code, first time on click of button it will throw error.. – Shubham pandey Feb 16 '22 at 16:05

Misha Mashina · Accepted Answer · 2022-02-17T06:15:00.157

0

If oldData keeps several objects, you can do: if(!oldData.includes(newData))

EDIT 1 (for original code in description): if both are just single objects, simple comparison will do: if(oldData! = newData)

EDIT 2 (for edited code in description):

addNewType(rowdata) {
    const newData = JSON.stringify(rowdata.value);
    const oldData = JSON.stringify(this.items.value);
    if(oldData.includes(newData)){
        console.log('This element already exists in the detail list');
    }
    else this.addItem(this.createItem(null));           
}

EDIT 3: if oldData has newData at least twice

addNewType(rowdata) {
    const newData = JSON.stringify(rowdata.value);
    const oldData = JSON.stringify(this.items.value);
    if((oldData.split(newData).length - 1) >= 2){
        console.log('This element already exists in the detail list at least TWICE');
    }
    else this.addItem(this.createItem(null));           
}

or:

addNewType(rowdata) {
    const newData = JSON.stringify(rowdata.value);
    const oldData = JSON.stringify(this.items.value);
    let newReg= new RegExp(newData, "g");
    if((oldData.match(newReg) || []).length >= 2){
        console.log('This element already exists in the detail list at least TWICE');
    }
    else this.addItem(this.createItem(null));           
}

edited Feb 17 '22 at 06:15

answered Feb 16 '22 at 13:32

Misha Mashina

1,739
2
4
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I have updated my code. Can u plz help to make it perfect – Shubham pandey Feb 16 '22 at 13:41
I want to push form only when new value not matched with old value – Shubham pandey Feb 16 '22 at 13:41
The previous version, with stringifying, offers you more flexiiblity. You just need to check if oldData includes new, and push to items only if it is not included. – Misha Mashina Feb 16 '22 at 13:44
Check EDIT 2 code. – Misha Mashina Feb 16 '22 at 18:16
I want if same object with values is available more than 1, than only error will come in console.log else this.addItem will execute. – Shubham pandey Feb 17 '22 at 05:35
This code will throw an error (or rather a console log atm) if it finds newData in oldData, so it will throw error however many times newData is inside oldData. Do you want to throw error exactly if newData is more than once found in oldData and *not* if it's there only as a single match? – Misha Mashina Feb 17 '22 at 06:00
Ok, added 2 more solutions as EDIT 3. – Misha Mashina Feb 17 '22 at 06:15

How to compare values of two objects in Angular

2 Answers2