How To Determine If Javascript Array Contains An Object With An Attribute That Is Equal To Each Other

I have an array like

selectedData = [{
   Name = 'Michelle', 
   LRN = '100011'
 },
 {
   Name = 'Micheal', 
   LRN = '100011'
 },
 {
   Name = 'Mick', 
   LRN = '100012'
 } // so on....
]

I am sending this array through a function and that simply checks if the LRN attribute of each object is same if not it throws error. I have written the function as -

createSet(selectedData) {
 this.selectedData.forEach (element => {
 //the condition
 }
 else
 {
  this.openSnackBar ("LRN mismatching");
 }
}

How do I check if the LRN attribute of each object is same? I don't want loop unless I have to. I'm working with more than thousand records. I appreciate all the help. :)

You could take Array#every and check the first item to each other. The method stops the iteration if the condition is false and returns then false, if not then true.

The callback's parameter can have three parts, one for the item, the next for the index and the third one has the reference to the array.

In this case only the item is used with a destructuring of LRN and the array. The unneeded index is denoted by an underscore, which is a valid variable name in Javascript.

if (!array.every(({ LRN }, _, a) => LRN === a[0].LRN)) {
    this.openSnackBar ("LRN mismatching");
}

Code with example of all property LRN having the same value.

const
    selectedData = [{ Name: 'Michelle', LRN: '100011' }, { Name: 'Micheal', LRN: '100011'}, { Name: 'Mick', LRN: '100011' }];

if (!selectedData.every(({ LRN }, _, a) => LRN === a[0].LRN)) {
    console.log("LRN mismatching");
} else {
    // just to show
    console.log('OK');
}

Mismatching

const
    selectedData = [{ Name: 'Michelle', LRN: '100011' }, { Name: 'Micheal', LRN: '100011'}, { Name: 'Mick', LRN: '100012' }];

if (!selectedData.every(({ LRN }, _, a) => LRN === a[0].LRN)) {
    console.log("LRN mismatching");
} else {
    // just to show
    console.log('OK');
}