js list modify in place code example

Example 1: modify array js

let newArray = oldArray.map(funcToEachElem);

Example 2: how to modify an array

let schedule = ['I', 'have', 'a', 'meeting', 'tommorrow'];
// removes 4 first elements and replace them with another
schedule.splice(0, 4, 'we', 'are', 'going', 'to', 'swim');
console.log(schedule); 
// ["we", "are", "going", "to", "swim", "tommorrow"]