deep_merge

deep_merge.js

'use strict';

function deepMerge(){
  let args = [].slice.call(arguments);
  let target = args.shift();
  let sources = args;
  if(sources.length == 0){
    return target;
  }
  else {
    let source = sources.shift();
    for(let key in source){
      if(!source.hasOwnProperty(key)){
        continue;
      }
      if(typeof source[key] == 'object'){
        if(!target.hasOwnProperty(key)){
          target[key] = {}
        }
        deepMerge(target[key],source[key]);
      }
      else {
        target[key] = source[key];
      }
    }
    sources.unshift(target)
    return deepMerge.apply(null,sources);
  }
}

let a = {'a': {'c':3},'d':4}
let b = {'a': {'d':4}}

let c = deepMerge({},a, b);
console.log(c)

'use strict';

function deepMerge(){
  let args = [].slice.call(arguments);
  let target = args.shift();
  let sources = args;
  if(sources.length == 0){
    return target;
  }
  else {
    let source = sources.shift();
    for(let key in source){
      if(!source.hasOwnProperty(key)){
        continue;
      }
      if(typeof source[key] == 'object'){
        if(!target.hasOwnProperty(key)){
          target[key] = {}
        }
        deepMerge(target[key],source[key]);
      }
      else {
        target[key] = source[key];
      }
    }
    sources.unshift(target)
    return deepMerge.apply(null,sources);
  }
}

let a = {'a': {'c':3},'d':4}
let b = {'a': {'d':4}}

let c = deepMerge({},a, b);
console.log(c)

if(typeof source[key] == 'object')

also need to check on null because typeof null === "object"