javascript - Angular 2: Populate checkbox list comparing two lists and initially check some items -

in angular 2 application in service file have following.

service.ts

getuserselections() {     return this.http.get('http://localhost:8080/selection/selections').map((res: response) => res.json()); }  getsavedselections() {     let params: urlsearchparams = new urlsearchparams();     params.set('access_token', localstorage.getitem('access_token'));     return this.http.get('http://localhost:8080/interest/user/selections', { search: params }).map((res: response) => res.json()); } 

getuserselections returns following json array.

[{     "key": "test1",     "val": 1.0   }, {     "key": "test2",     "val": 1.0   }, {     "key": "test3",     "val": 1.0   }] 

getsavedselections returns following.

[{     "key": "test2",     "val": 1.0   }, {     "key": "test3",     "val": 1.0   }] 

i don't need call these 2 services separately. once call getuserselection need call both 1 after other if first service success. want compare these 2 json arrays, 1st array includes items, 2nd 1 includes items 1st array. need check items included in 2nd array , add new attribute "selected (true or false)" items of 1st array. ultimately, need return 1 array below.

[{     "key": "test1",     "val": 1.0,     "selected": false   }, {     "key": "test2",     "val": 1.0,     "selected": true   }, {     "key": "test3",     "val": 1.0,     "selected": true   }] 

any suggestions highly appreciated.

you use map function on first array. return new array callback function called on each item.

let result = array1.map((elem1) => {   elem1.selected = false;   array2.foreach((elem2) => {     if (elem2.key === elem1.key)       elem1.selected = true;   });   return elem1; });