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Deeper Destructuring, destructuring functions, and pitfalls

Deeper Destructuring, destructuring functions, and pitfalls

using default values and assigning undefined in destructuring

Destructuring objects and arrays in any depth is possible. We can also use default values. Objects or arrays that don’t exist on the right become assigned to undefined on the left.

Node.js
let user = {
    name        : 'Ashley',
    email       : 'ashley@ilovees2015.net',
    lessonsSeen : [ 2, 5, 6, 7, 9 ],
    nextLesson  : 10
};
let { 
    lessonsSeen : [ 
        first, 
        second, 
        third, 
        fourth, 
        fifth, 
        sixth = null, 
        seventh 
    ], 
    nextLesson : eighth 
} = user;
console.log( "first:\t\t"+first+"\nsecond:\t\t"+second+"\nthird:\t\t"+third+
              "\nfourth:\t\t"+fourth+"\nfifth:\t\t"+fifth+"\nsixth:\t\t"+sixth+
              "\nseventh:\t"+seventh+"\neighth:\t\t"+eighth);

Notice that the null ...