Pfthb

I wanted to deep copy some objects in javascript so that my reducer is pure in redux. Some properties have 1 level of nesting and some have 2 and some have 3 like:

var x = a:9, y:a:b:9, z = a:b:c:9;

So should I use some other technique like:

var newX = ...x, newY = a:...y.a

Should I continue to use the same technique in a loop - write my custom deep copy for 3 level nesting also or should I simply use:

var newZ = JSON.parse(JSON.stringify(z));

to create my deep copy.

What is the fastest way alternative to JSON.parse(JSON.stringify(value))??

If you truly want deep cloning, the most performant way by far in my experience is the JSON parse/stringify trick you already mentioned.

Otherwise you'll have to fall back to some sort of recursive cloning strategy. Lodash has a deepClone function for example.

As an alternative to deep cloning, I highly recommend immer, which leverages a concept called structural sharing, in which unchanged parts of the object aren't cloned. This is more performant and uses less memory.

I use this function found somewhere on StackOverflow:

const deepCopy = origin => 
 let cp;
 switch (typeof origin) 
 case 'object':
 if (origin === null) 
 cp = null;
 else 
 switch (toString.call(origin)) 
 case '[object Array]':
 cp = origin.map(deepCopy);
 break;
 case '[object Date]':
 cp = new Date(origin);
 break;
 case '[object ReqExp]':
 cp = new RegExp(origin);
 break;

 default:
 cp = Object.keys(origin).reduce((prev, key) => 
 prev[key] = deepCopy(origin[key]);
 return prev;
 , );
 break;
 
 
 break;

 default:
 cp = origin;

 
 return cp;