How to join two JavaScript Objects without using JQUERY

Question

I have two json objects obj1 and obj2  i want to merge them and crete a single json object  The resultant json should have all the values from obj2 and the values from obj1 which is not present in obj2   Question   var obj1          name   manu        age  23       occupation   SE     var obj2          name   manu        age  23       country   india     Expected   var result          name   manu        age  23       occupation   SE        country   india

User · Answer

1    var merged       for key in obj1      merged key    obj1 key   for key in obj2      merged key    obj2 key       2   var merged       Object keys obj1  forEach k   gt  merged k    obj1 k    Object keys obj2  forEach k   gt  merged k    obj2 k      OR  Object keys obj1       concat Object keys obj2        forEach k   gt  merged k    k in obj2   obj2 k    obj1 k        3  Simplest way   var merged       Object assign merged  obj1  obj2

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Just another solution using underscore js     extend     obj1  obj2

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This simple function recursively merges JSON objects  please notice that this function merges all JSON into first param  target   if you need new object modify this code   var mergeJSON   function  target  add        function isObject obj            if  typeof obj     object                 for  var key in obj                    if  obj hasOwnProperty key                         return true     search for first object prop                                                   return false            for  var key in add            if  add hasOwnProperty key                 if  target key   amp  amp  isObject target key    amp  amp  isObject add key                      this mergeJSON target key   add key                  else                   target key    add key                                     return target       BTW instead of isObject   function may be used condition like this   JSON stringify add key   0           but this is not good solution  because it s will take a lot of resources if we have large JSON objects

User · Answer

I ve used this function to merge objects in the past  I use it to add or update existing properties on obj1 with values from obj2   var  mergeRecursive   function obj1  obj2             iterate over all the properties in the object which is being consumed       for  var p in obj2                 Property in destination object set  update its value            if   obj2 hasOwnProperty p   amp  amp  typeof obj1 p       undefined                   mergeRecursive obj1 p   obj2 p                 else                 We don t have that level in the heirarchy so add it             obj1 p    obj2 p                           It will handle multiple levels of hierarchy as well as single level objects  I used it as part of a utility library for manipulating JSON objects  You can find it here

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WORKING FIDDLE  Simplest Way with Jquery -  var finalObj     extend obj1  obj2     Without Jquery -  var finalobj     for var  obj in obj1  finalobj  obj   obj1  obj   for var  obj in obj2  finalobj  obj   obj2  obj

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There are couple of different solutions to achieve this     1 - Native javascript for-in loop   const result       let key   for  key in obj1      if obj1 hasOwnProperty key        result key    obj1 key          for  key in obj2      if obj2 hasOwnProperty key        result key    obj2 key           2 - Object keys     const result        Object keys obj1     forEach key   gt  result key    obj1 key     Object keys obj2     forEach key   gt  result key    obj2 key      3 - Object assign     Browser compatibility  Chrome  45  Firefox  Gecko   34  Internet Explorer  No support  Edge   Yes   Opera  32  Safari  9     const result   Object assign     obj1  obj2     4 - Spread Operator  Standardised from ECMAScript 2015  6th Edition  ECMA-262       Defined in several sections of the specification  Array Initializer  Argument Lists   Using this new syntax you could join merge different objects into one object like this   const result          obj1       obj2       5 - jQuery extend target  obj1  obj2    Merge the contents of two or more objects together into the first object   const target          extend target  obj1  obj2     6 - jQuery extend true  target  obj1  obj2    Run a deep merge of the contents of two or more objects together into the target  Passing false for the first argument is not supported   const target          extend true  target  obj1  obj2     7 - Lodash   assignIn object   sources    also named as   extend   const result          assignIn result  obj1  obj2     8 - Lodash   merge object   sources     const result     merge obj1  obj2     There are a couple of important differences between lodash s merge function and Object assign   1- Although they both receive any number of objects but lodash s merge apply a deep merge of those objects but Object assign only merges the first level  For instance     isEqual   merge     x        y    key1   value1                 x        y    key2   value2                  x        y          key1   value1         key2   value2                      true   BUT   const result   Object assign     x        y    key1   value1                 x        y    key2   value2                isEqual result      x        y          key1   value1         key2   value2                      false    AND   isEqual result      x        y          key2   value2                      true   2- Another difference has to do with how Object assign and   merge interpret the undefined value     isEqual   merge  x  1    x  undefined      x  1       false   BUT     isEqual Object assign  x  1    x  undefined      x  undefined      true     Update 1   When using for in loop in JavaScript  we should be aware of our environment specially the possible prototype changes in the JavaScript types  For instance some of the older JavaScript libraries add new stuff to Array prototype or even Object prototype  To safeguard your iterations over from the added stuff we could use object hasOwnProperty key  to mke sure the key is actually part of the object you are iterating over     Update 2      I updated my answer and added the solution number 4  which is a new JavaScript feature but not completely standardized yet  I am using it with Babeljs which is a compiler for writing next generation JavaScript     Update 3  I added the difference between Object assign and   merge

[javascript] How to join two JavaScript Objects, without using JQUERY

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