Im filtering menu array by permission once user logged in.
Im generating static menu and then give copy of array to filter.
constructor(public menu: MenuService, public permissionService: PermissionService) {
console.log(menu.getMenu()) // this changes after filtering below
this.menuItems = this.permissionService.filterMenuByTopic([...menu.getMenu()]); // here I'm using a copy
}
Why do this happen? If I have used spread operator and I do not use original array [...menu.getMenu()]
.
Only If I refresh the pages menu.getMenu()
returns to original value
UPD 1
answering to the comments, here is getMenu() func
import { Injectable } from '@angular/core';
@Injectable()
export class MenuService {
menuItems: Array<any>;
constructor() {
this.menuItems = [];
}
addMenu(items: Array<{
text: string,
heading?: boolean,
link?: string, // internal route links
elink?: string, // used only for external links
target?: string, // anchor target="_blank|_self|_parent|_top|framename"
icon?: string,
alert?: string,
submenu?: Array<any>
}>) {
items.forEach((item) => {
this.menuItems.push(item);
});
}
getMenu() {
return this.menuItems;
}
}
The spread operator creates a shallow copy. If the content of a menu was objects, then changing those objects in a copy array will change those objects in the original array (or technically, those two references are for the same object):
const obj1 = { val: 1 } const obj2 = { val: 2 } const obj3 = { val: 3 } const arr = [obj1, obj2, obj3] // creating a copy with the spread operator const copy = [...arr] // changing the second element in the copy copy[1].val = 22 // the element in the original array is changed too console.log(arr)
Thanks to Ivan's comment
I've made a deep clone by following
const cloned = menu.getMenu().map(x => Object.assign({}, x));
console.log('cloned ', cloned)
this.menuItems = this.permissionService.filterMenuByTopic(cloned);
One of the answer I have found here link
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