delete myArray[key];

const index = myArray.indexOf(key, 0);
if (index > -1) {
   myArray.splice(index, 1);
}

let foo_object // Item to remove
this.foo_objects = this.foo_objects.filter(obj => obj !== foo_object);

removeDocument(doc){
   this.documents.forEach( (item, index) => {
     if(item === doc) this.documents.splice(index,1);
   });
}

onDelete(id: number) {
    this.service.delete(id).then(() => {
        let index = this.documents.findIndex(d => d.id === id); //find index in your array
        this.documents.splice(index, 1);//remove element from array
    });

    event.stopPropagation();
}

arr.splice(2,1);

arr.splice(arr.length,1);

// Your key
const key = 'two';

// Your array
const arr = [
    'one',
    'two',
    'three'
];

// Get either the index or -1
const index = arr.indexOf(key); // returns 0


// Despite a real index, or -1, use spread operator and Array.prototype.slice()
const newArray = (index > -1) ? [
    ...arr.slice(0, index),
    ...arr.slice(index + 1)
] : arr;

let updatedArray = [];
for (let el of this.oldArray) {
    if (el !== elementToRemove) {
        updated.push(el);
    }
}
this.oldArray = updated;

departments: string[] = [];

 removeDepartment(name: string): void {
    this.departments = this.departments.filter(item => item != name);
  }