Complete Understanding of the Classic Mode of js object creation, and comprehensive understanding of js

Complete Understanding of the Classic Mode of js object creation, and comprehensive understanding of js

1. Overview

Create an object through the constructor, and sometimes forget to write new, then the function will return undefined

You can create a createXXX function and encapsulate new in the system.

Function Student (props) {this. name = props. name | 'anonymous'; this. grade = props. grade | 1;} Student. prototype. hello = function () {alert ('hello, '+ this. name + '! ');} Function createStudent (props) {return new Student (props | | {});}

NOTE: If return xxx is not displayed in the function, undefined is returned.

Example

Use the constructor to define Cat and make all Cat objects have a name attribute, share a method say (), and return the string 'hello, xxx! ':

'Use strict '; function Cat (name) {this. name = name;} Cat. prototype. say = function () {return ('hello, '+ this. name + '! ');} // Test: var kitty = new Cat ('Kitty'); var doraemon = new Cat ('doradream'); if (Kitty & kitty. name = 'Kitty '& Kitty. say & typeof kitty. say = 'function' & kitty. say () = 'hello, Kitty! '& Kitty. say === doraemon. say) {alert (' test passed! ');} Else {alert (' test failed! ');}

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