How do I backup or clone an array of objects in typescript? [closed]

I have tried all the examples listed here, and no matter which one I take including the JSON parse / stringify, when I modify an element in the original array, it is automatically reflected in the backup as is the case in a copy by reference. I need to find a way to break the link and reliably back up by value.

        this.backupPersons = JSON.parse(JSON.stringify(this.persons));

        this.backupPersons = this.persons.slice(0);

        this.backupPersons = this.persons.concat();

        this.backupPersons.concat(this.persons);

        this.backupPersons = angular.copy(this.persons);

        for (var i in this.persons) {
            this.backupPersons.concat(this.persons[i]);
        }

        this.persons.forEach(function (arrayItem) {
            this.backupPersons.concat(arrayItem);
        });

        for (const element of this.persons) {
            this.backupPersons.push(element);
          }