Recursion, shallow copy and deep copy in Javascript

recursive

What is recursion?

A function is recursive if it can call itself internally. A recursive function is a function that calls itself internally

Recursive functions function as loops because recursion is prone to “stackoverflow” errors, an exit conditional return must be added.

function fn(num) {
  console.log(num);
  if (num > 10) {return num;
      } 
  else{
      num++;
      fn(num);
      };

}
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Shallow copy Object.assign(newObj, targetObj)

var o = {
  id: 1.name: "Car".product: {
    id: 2.name: "Refrigerator",}};var obj = {};
Object.assign(obj, o); // copy o shallow to obj
console.log(obj);/ / {id: 1, name: 'cars' product: {id: 2, name:' fridge}}
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A shallow copy is only a copy of one layer. When the property inside the object is also an object, the property object assigns the address to the copied object.

Deep copy

var o = {
  id: 1.name: "Car".product: {
    id: 2.name: "Refrigerator",}};var obj = {};
function deepCopy(newObj, targetObj) {
  for (var k in targetObj) {
    if (targetObj[k] instanceof Array) {   // Since arrays are also objects, we need to put array judgment first
      newObj[k] = [];  
      deepCopy(newObj[k], targetObj[k]);
    } else if (targetObj[k] instanceof Object) {
      newObj[k] = {};
      deepCopy(newObj[k], targetObj[k]);
    } else {
      newObj[k] = targetObj[k];
    }
  }
}
deepCopy(obj, o);
console.log(obj);

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