SOURCE

let arr = [1, 2, 3, { 'name': 'tom' }];

// let arr1 = arr;
// let arr2 = arr.slice();

// console.log(arr1);
// console.log(arr2);
// arr[0]=999;
// arr[3].name = 'jerry';
// console.log(arr1);
// console.log(arr2);

function shallow(target) {
    let cloneTarget = (Array.isArray(target)) ? [] : {};
    for (key in target) {
        cloneTarget[key] = target[key];
    }
    return cloneTarget;
}

function deep(target) {
    let cloneTarget = (Array.isArray(target)) ? [] : {};
    for (key in target) {
        if(target[key] instanceof Object){
            cloneTarget[key] = deep(target[key]);
        } else
            cloneTarget[key] = target[key];
    }
    return cloneTarget;
}

arr1 = shallow(arr);
arr2 = deep(arr);
arr3 = JSON.parse(JSON.stringify(arr));
arr[0] = 999;
arr[3].name = 'jerry';

console.log(arr1);
console.log(arr2);
console.log(arr3);