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This article mainly introduces "how to use the new target attribute in ES6". In the daily operation, I believe that many people have doubts about how to use the new target attribute in ES6. The editor consulted all kinds of materials and sorted out a simple and easy-to-use method of operation. I hope it will be helpful to answer the question of "how to use the new target attribute in ES6". Next, please follow the editor to study!

New is the command for the constructor to generate the instance, and ES6 introduces the new.target attribute for the new command. This property is used to determine how the constructor is called. In the constructor, new.target returns undefined if a constructor is not called through the new operator.

The new.target attribute uses the scene

If a constructor does not generate an instance through the new command, it will report an error.

This is done in es5:

FunctionShape (options) {

If (thisinstanceofShape) {

This.options=options

} else {

/ / or manually create an instance for it and return

/ / returnnewShape (options)

/ / either remind me

ThrownewError ('Shape constructor must use the new operator')

}

}

You can do this in es6:

FunctionShape (options) {

/ / if (new.targetkeeper assigned undefined') {} you must use new.target in constructor, where an error will be reported.

Constructor (options) {

If (new.targetcargo assigned undefined) {

This.options=options

} else {

ThrownewError ('must use the new operator')

}

}

}

The above code can determine whether the return is undefined through the new.target attribute to know whether the constructor is called through the new operator.

How to use the new.target property

A constructor can only be used for subclass inheritance and cannot new itself.

New.target, when the subclass inherits the parent class, returns the constructor name of the subclass.

ClassParent {

Constructor () {

Console.log (new.target)

}

}

ClassChildextendsParent {

Constructor () {

Super ()

}

}

/ / Child

At this point, the study on "how to use the new target attribute in ES6" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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