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This article will explain in detail what new methods there are in javascript. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

The new method of javascript object: 1, "Object.is ()", which can be used to compare whether the two values are strictly equal; 2, "Object.assign ()", which can be used to merge objects and copy all enumerable properties of the source object to the target object.

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

New method of javascript object

1. Object.is ()

In es6, there are three ways to compare whether two values are strictly equal, using the equality operator'= =', the strict equality operator'=', or the Object.is () method, but the first two methods are flawed and cannot be used in some special scenarios, while Object.is () does not.

The behavior of Object.is () and'= 'operators is basically the same.

But there are two differences:

(1) + 0 is not equal to-0

(2) NaN equals itself

2. Object.assign ()

(1) Object.assign () is used for merging objects to copy all enumerable attributes of the source object to the target object.

(2) the first parameter of the Object.assign () method is the target object, and the subsequent parameters are the source object.

If the destination object has an attribute with the same name as the source object, or if more than one source object has an attribute with the same name, the following properties override the previous properties.

You can see that b: 2 in two covers b: 1 in one, c: 3 in three covers c: 2 in two.

(3) if there is only one parameter, Object.assign () will return the parameter directly.

(4) if the parameter is not an object, it will be converted to an object and then returned.

You can see that Object.assign () converts the number 5 into a Number object and returns

(5) undefined and null cannot be converted into objects, and an error will be reported if they are used as parameters.

If a non-object parameter appears at the location of the source object (that is, not the first parameter), the processing rules are different. These parameters are converted to objects, or skipped if they cannot be converted to objects. This means that undefined and null will not report an error if they are not the first parameter, as shown below

Other types of values (that is, numeric, string, and Boolean values) are not in the first parameter (that is, the first parameter) and will not report an error. However, none of the values have any effect except that the string is copied into the target object as an array.

In the above code, v1 v2 v3 is a string, a Boolean value, and a numeric value, respectively. As a result, only the string is merged into the target object (in the form of a character array), and both numeric and Boolean values are ignored. This is because only a wrapper object with a string produces enumerable properties.

(6) convert Boolean values, numeric values, and strings to the corresponding wrapper object, respectively, and you can see that their original values are all on the wrapper object's internal attribute [[PrimitiveValue]], which will not be copied by Object.assign (). Only the wrapper object of the string produces enumerable semantic properties, and those properties are copied.

The attributes copied by Object.assign () are limited. Only the attributes of the shell source object are copied (no inherited attributes are copied).

Non-enumerable attributes (enumerable: false) are also not copied.

This is the end of this article on "what new methods are added in javascript". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it out for more people to see.

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