NG4 - Add one new key value and remove existing key valye from Object of Array [object, object ]

NG4 - Add one new key value and remove existing key valye from Object of Array [object, object ]
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InitialArray = [{"key1":"val1", "key2": "val2"}, {"key1":"val11","key2":"val21"}]

Drop Key1/val1 and add Key3/Val3 

ExpctedArray =  [{"key3":"val3", "key2": "val2"}, {"key3":"val31","key2":"val21"}]

Using Angular4/2 Arrow fundtion with ForEach Loop

this.InitialArray.forEach(el => {
        var existingObject = el;
//delete existingObject["key1"];
delete existingObject.key1;
Object.assign(existingObject, {
key3:this.valu3   //'valu3' in this.valu3. Key3 no need of 'key3' Quotes (')
});
   });


NG4- add/ Remove one more key value of Existing object
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With the new ES6 method Object.assign, much of the repeated boilerplate can be eliminated. Example:

var existingObject = {
    firstValue: 'hello'
};

/* some time later... */

Object.assign(existingObject, {
  secondValue: 'world' });
  
Ref: https://stackoverflow.com/questions/25777499/short-hand-to-add-many-key-value-pairs-to-an-existing-javascript-object

Remove:
------
// Example 1
var key = "Cow";
delete thisIsObject[key]; 

// Example 2
delete thisIsObject["Cow"];

// Example 3
delete thisIsObject.Cow;

If a JavaScript shell, it's as easy as:

delete object.keyname;

Ref: https://stackoverflow.com/questions/3455405/how-do-i-remove-a-key-from-a-javascript-object