Merge objects in JavaScript -

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• how deep merge instead of shallow merge? 16 answers

i have 2 objects , want merge them, should not replace object.

var x = {'one':1, 'two': {'b': 2, 'c': 3}} var y = {'two': {'b': 4}} 

when merge them out put should :

{'one':1, 'two': {'b': 4, 'c': 3}} 

you can use recursive approach updating nested object.

var x = {    'one': 1,    'two': {      'b': 2,      'c': 3    }  }  var y = {    'two': {      'b': 4    }  }      function merge(a, b) {  // create new object , copy properties of first 1    var res = object.assign({}, a);    //iterate on keys of second object    object.keys(b).foreach(function(e) {      // check key present in first object      // check type of both value object(not array) ,      // recursively call function      if (e in res && typeof res[e] == 'object' && typeof res[e] == 'object' && !(array.isarray(res[e]) || array.isarray(b[e]))) {     // recursively call function , update value      // returned ne object     res[e] = merge(res[e], b[e]);      } else {        // otherwise define preperty directly        res[e] = b[e];      }    });    return res;  }    var res = merge(x, y);    console.log(res);

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update : if want merge array need this.

var x = {    'one': 1,    'two': {      'b': [22, 23],      'c': 3    }  }  var y = {    'two': {      'b': [24]    }  }      function merge(a, b) {    var res = object.assign({}, a);    object.keys(b).foreach(function(e) {      if (e in res && typeof res[e] == 'object' && typeof res[e] == 'object' && !(array.isarray(res[e]) || array.isarray(b[e]))) {        res[e] = merge(res[e], b[e]);        // in case both values array       } else if (array.isarray(res[e]) && array.isarray(b[e])) {        // push values in second object        [].push.apply(res[e], b[e]);        // or use         // res[e] = res[e].concat(b[e]);      } else {        res[e] = b[e];      }    });    return res;  }    var res = merge(x, y);    console.log(res);