Set data constructor

Set data structure , It's like an array , All the data is unique , There are no duplicate values , It's itself a constructor , Mainly used for weight removal , But it must be converted into an array , Let's learn the following two methods of transforming true arrays .

The first one is :Array.from

The second kind : Extension operators ：...

Use the expansion operator to put set Set will string an , Get a set of class arrays

In use and expansion Operator to convert to a real array

Add :Array.prototype.slice.call() In this way, it is converted into an array , It's not really an array , It is more suitable to turn the set of parameters in a function into an array

 

Use the expansion operator to realize the combination of two arrays

Put the passed parameters , Make an array

Pass two parameters ：

Be careful : If there is only one parameter or no parameter is passed , Returns the undefined Or an empty array

Set Properties and methods of :

size  Get the length of the array , The return value is the length of the data

add()  Add a value , return Set Structure itself .

delete()  Delete a value , Returns a Boolean value ,ture Indicates that the deletion was successful ,fales It means unsuccessful or unable to find

has()  Find a piece of data , Returns a Boolean value ,ture Said to find ,fales It said that it was not found

clear()  Clear all members , Because it cleared , So there is no return value

Deconstruction and assignment of arrays

The value in the array will be automatically parsed into the corresponding variable that accepts the value , The deconstruction and assignment of an array should correspond one by one , If there's one that doesn't correspond, it's undefined

Object's deconstruction assignment

An important difference between object deconstruction and array , The elements of an array are ordered , The value of a variable is determined by its position , The properties of an object have no order , Variable must have the same name as property , To get the right value

  Change the name of the deconstructed variable

Add default values to the deconstructed variables

Solve the problem of missing assignment , When the attribute in the object is undefined Or no attributes , The variable will be assigned the default value

set Constructor's for of loop , Can traverse array