Let's say we have an array of object:
var obj = [{a: 1, b: 2, c: 3, d: 4, e: 5 },{a: 6, b: 7, c:
8, d: 9, e: 0 }];
and we want to delete key c,e from both of the objects.
How can it be done? One of the methods I found is:
['c', 'e'].forEach(e => delete obj[e]); //for object
Is there any other way so we don't have to use double for loop.
One way to do it is to use .map() together with object destructuring:
var obj = [
{ a: 1, b: 2, c: 3, d: 4, e: 5 },
{ a: 6, b: 7, c: 8, d: 9, e: 0 },
];
var newObj = obj.map(({ c, e, ...rest }) => rest);
console.log(newObj)This will create a new array with new objects which contain all of the other keys except for c and e.
({ c, e, ...rest }) will get c and e and store them in separate variables and all other properties will be stored in new object named rest. This is what the above syntax means
const {c, e} = {a:1, c: 2, e: 3}), you can choose the variables you want to pick out of the object. The ... in there is called "rest" and all other keys which were not explicitly picked out are stored in that object. The name of the variable can be anything, it doesn't have to be "rest".
...rest simply collects all the "rest", i. e. the remaining properties of the destructured object - after c and e had been removed and places them together again in an object called rest.You have 2 options to resolve it:
map(({ a,b,c,d,e }) => ({a,b,d}){ c, e, ...rest }Object destructuring like below
const obj = { a: 1, b: 2, c: 3, d: 4, e: 5 } var {c, e} = obj; // c = 3, e = 5
With option 2, you will have c,e implicit name and the remaining items named rest. After that, you just need to get rest items.
Option 1
var obj =
[
{ a: 1, b: 2, c: 3, d: 4, e: 5 },
{ a: 6, b: 7, c: 8, d: 9, e: 0 },
];
console.log(obj.map(({ a,b,c,d,e }) => ({a,b,d})));Option 2
var obj =
[
{ a: 1, b: 2, c: 3, d: 4, e: 5 },
{ a: 6, b: 7, c: 8, d: 9, e: 0 },
];
console.log(obj.map(({ c, e, ...rest }) => rest));
// ...rest: the same as `a,b,d`
obj.map(({ c, e, ...rest }) => rest)would create a new array of new objects with those keys removed.['c', 'e']is actually not known at build, only runtime).