obj['New key'] = obj['old key'];

// JavaScript Program to illustrate renaming
 
// Creating an object 'capital' with
// key "Burma" and value "Naypitaw"
let capitals = [{ 
    "Burma": "Naypyitaw"
}];
 
console.log(capitals);
 
// Function to rename on button click
function rename() { 
    capitals = capitals.map(function (obj) {
 
        // Assign new key
        obj['Myanmar'] = obj['Burma']; 
 
        // Delete old key
        delete obj['Burma']; 
 
        return obj;
    });
    console.log(capitals);
}
 
rename();

[ { Burma: 'Naypyitaw' } ]
[ { Myanmar: 'Naypyitaw' } ]

Object.defineProperty(obj, key, description) 

// JavaScript Program to illustrate renaming key
 
// Creating an object 'capital' with
// key "Persia" and value "Tehran"
let capitals = [{
    "Persia": "Tehran"
}];
console.log(capitals);
 
// Function to rename old key
function renameKey(obj, old_key, new_key) {
 
    // Check if old key = new key
    if (old_key !== new_key) {
 
        // Modify old key
        Object.defineProperty(obj, new_key,
 
            // Fetch description from object
            Object.getOwnPropertyDescriptor(obj, old_key));
 
        // Delete old key
        delete obj[old_key];
    }
}
function rename() {
    capitals.forEach(obj => renameKey(obj, 'Persia', 'Iran'));
    console.log(capitals);
}
 
rename();

[ { Persia: 'Tehran' } ]
[ { Iran: 'Tehran' } ]