CODE EXAMPLE FOR JAVASCRIPT

deep copying object

// NORMAL COPY---------------------------------------
const a = { x: 0}
const b = a;
b.x = 1; // also updates a.x

// SHALLOW COPY---------------------------------------
const a = { x: 0, y: { z: 0 } };
const b = {...a}; // or const b = Object.assign({}, a);

b.x = 1; // doesn't update a.x
b.y.z = 1; // also updates a.y.z

// DEEP COPY---------------------------------------
const a = { x: 0, y: { z: 0 } };
const b = JSON.parse(JSON.stringify(a)); 

b.y.z = 1; // doesn't update a.y.z