Объединить объекты в Javasript
Объект — это непримитивный тип данных, который позволяет нам хранить данные в парах ключ-значение.
Please enable JavaScript
В этом руководстве мы объединим два или более объекта в JavaScript, используя разные методы.
Используйте функцию object.assign() для объединения объектов в JavaScript
В JavaScript метод assign() может итеративно считывать свойства одного или нескольких объектов в целевой объект. Возвращает целевой объект. Мы можем передать два объекта с пустым объектом, чтобы объединить их.
Проверьте код ниже.
Используйте оператор Spread для объединения объектов в JavaScript
В JavaScript оператор распространения (…) может распаковывать все элементы массива. Мы также можем использовать его для объединения объектов.
См. Следующий код о том, как использовать этот метод.
Используйте функцию array.reduce() для объединения объектов в JavaScript
Здесь мы использовали функцию array.reduce() , которая используется для реализации функции-редуктора (которую вы предоставляете) для каждого элемента в массиве. Он возвращает одно выходное значение.
Мы реализуем это в следующем фрагменте кода.
Используйте функцию jquery.extend() для объединения объектов в JavaScript
jQuery — это легкая и очень быстрая библиотека JavaScript. Это упрощает использование JavaScript.
extend() — это метод jQuery, используемый для объединения двух или более объектов в объект. Он возвращает объект.
Например,
Использование пользовательской функции для объединения объектов в JavaScript
Здесь мы создаем нашу собственную функцию для возврата объединенного объекта. Он использует свойства двух объектов, которые объединены в третий объект.
Merging JavaScript Objects
A short guide to creating a new object from multiple objects.
This guide will show you how to merge two or more JavaScript objects into a new object. The new object will contain the properties of all the objects that were merged together. JavaScript provides multiple ways to accomplish this task with a lot of different methods. Here, we will take a look at three of the more popular approaches. These are:
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— The spread (…) operator — The Object.assign() method — Object loop method (for…in)
Spread Operator
The spread operator was introduced with ES6 and allows us to merge multiple arguments or objects and returns a new combined value anywhere defined in your code.
If any of the objects or values added to the spread operation share the same property or name (e.g. “firstName”), the last one passed into your operation will be the value taken and overwrites any earlier values with the same key when creating your new object. This can be seen in our example above.
One important factor in using this approach is that the shape of your final value is defined by the wrapping characters. That is, we use the opening and closing braces (“< >”) to determine the resulting shape of our action, in this case, an object. Another result shape we can use are brackets (“[ ]”) when combining arrays to create a new array.
Object.assign()
The object prototype method “assign” is a tried and true method introduced with ES5. The spread operator has since taken over to do the same thing, but if you don’t have browser support for the latest and greatest, or you have to support older browsers, the assign method may be your go to in these niche situations.
In the code shown above, the assign method takes one or many arguments just like the spread operator. Just like the spread operator, if we need to define and default or ending shape of our variable, we add in an empty object `<>` that the following objects will fill into.
Object Loops (for…in)
Our final method for merging objects are loops. This is an older method and is not nearly as popular as spread and assign, but it does come with some convenient customizations if you need more granular control over how your objects will be merged. We’ll upgrade it slightly to use some ES6 flavoring (for…in, and reduce) while we’re at it. No need to stay old school in everything, right?
We can see in the code above that we first loop over the passed in object(s). In this case we are making use of the rest parameter syntax in our function parameters. Then we loop over each object and it’s keys in order to create our final object.
One important note to remember is that when JavaScript merges your objects and values into a new object, this is considered a shallow copy. This means that top level values contain no reference to the old objects values, whereas deeper or nested values may contain a reference to the original object. If you update our newly created object, old object references may update as well!
There are some verbose examples of what are called “deep copying” functions provided by different libraries and individuals (e.g. jQuery.extend(), lodash, underscore, JSON.parse(JSON.stringify), etc…). Be warned that these are expensive operations. Doing deep copies over large lists of data could highly impact user experience and performance on the device running your code! If you find yourself doing this a lot or wanting to do this a lot, take a step back and think about the architecture of your code and decide if there is a more DRY or maintainable way to break apart and manage your code’s state.
Conclusion
Whichever is best for your project is the best approach for you! Which browsers you need support will be one of the main factors in the choice you make between these and other solutions. If you are only supporting the latest and greatest browsers, you will probably end up using the spread operator a lot more than the others. On the other hand, if you have to want that granularity or old browser support, you may fall back to manual loops. Sometimes, it’s about what your team decides to use to be consistent with each other. In the end, it’s all up to you!
How to join two JavaScript Objects, without using JQUERY [duplicate]
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.
6 Answers 6
There are couple of different solutions to achieve this:
1 — Native javascript for-in loop:
3 — Object.assign() :
(Browser compatibility: Chrome: 45, Firefox (Gecko): 34, Internet Explorer: No support, Edge: (Yes), Opera: 32, Safari: 9)
Using this new syntax you could join/merge different objects into one object like this:
Merge the contents of two or more objects together into the first object.
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.
7 — Lodash _.assignIn(object, [sources]) : also named as _.extend :
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:
2- Another difference has to do with how Object.assign and _.merge interpret the undefined value:
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.
How to merge two objects in JavaScript
The Object.assign(target, source1, soure2, . ) method was introduced in ES6. It copies all enumerable own properties of one or more source objects to a target object and returns the target object.
The following example uses Object.assign() to merge the profile and job objects into the user object:
There is no limit to the number of objects you can merge with Object.assign() .
All source objects get merged into the first object. Only the target object is mutated and returned.
If you don’t want to mutate the target object, just pass an empty object <> as a target:
The properties are overwritten by other objects that have the same properties later in the order of the parameters:
Read this guide to learn more about the Object.assign() method.
Spread Operator
ES6 introduced the spread operator ( . ) that can also be used to merge two or more objects to create a new one that has properties of the merged objects.
Note: Spread operators were first introduced in ES6 (ECMAScript 2015) but object literal spread support was added in ES9 (ECMAScript 2018).
Here is an example that uses object spread syntax to merge two objects:
The object spread is a relatively new feature and only works in the latest versions of modern browsers. Similar to Object.assign() , it allows you to merge any number of objects with the identical handling of duplicate keys.
Custom Function
You can also write your own custom function to merge two or more objects:
Deep Merge Objects
To deep merge two or more objects, you need to recursively copy all objects’ own properties, nested arrays, functions, and extended properties to the target object.
Let us extend the above function to perform a deep merger of multiple objects:
Lodash merge() Method
You can also use Lodash’s merge() method to perform a deep merger of objects. This method recursively merges two or more source objects’ properties into a target object:
To learn more about JavaScript objects, prototypes, and classes, read this guide.
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