Lab Notes on Constructors and prototypes

For constructor, I think of an example. B was born of B, but B cut off his mother-child relationship. A had no children and decided to adopt B. So A became B's stepmother, that is, B's legal mother. If you ask B's mother what is called, it is equivalent to asking B who is the constructor. This relationship can easily be changed. Just set up a document or proof. The prototype is equivalent to B's genes, which cannot be changed due to adoption. Unless all its genes have been changed, then it is natural that B is its mother-in-law.

// School function School (name) {this. name = name; this. teachers = []; this. level = function () {console. log ('university ') }}// attribute School added to the prototype. prototype. students = []; // School function -- introduces School. prototype. show = function () {console. log (this. name + ': Great school! ') This. teachers. forEach (function (teach) {console. log (this. name + '-' + teach);}) // School function --- recruitment Instructor School. prototype. recruit = function (name) {this. teachers. push (name);} // School function --- enrollment School. prototype. enroll = function (name) {this. students. push (name) ;}// create the object var ts = new School ('Tsinghua University ') by using the constructor '); // at this time, School is the ts constructor var bj = new School ('beijin University '); // at this time, School is the object created by the constructor of bj, note two questions // 1 The properties and methods in the constructor are not shared. // 2 the properties and methods on the prototype are shared. ts. recruit ('frog'); // frog is the teacher bj of ts. recruit ('Aaron '); // Aaron is the teacher of bj's school ts. show (); // frog only appears in ts bj. show (); // Aaron only appears in bj. // The attributes declared in the constructor are not shared with the console. log (bj. teachers = ts. teachers); // false // The methods declared in the constructor are not shared with the console. log (bj. level = ts. level); // false; // it indicates that teachers is correct in the constructor. teachers in different schools do not affect ts. enroll ('Tom '); // only provides the ts school enrollment console. log (bj. students) // ts school does not enroll students This student also exists bj. enroll ('jek'); console. log (ts. students) // for students recruited by bj, the prototype is also available in ts. // The prototype method is shared console. log (bj. enroll = ts. enroll) // true // indicates that the prototype property is a shared console. log (bj. students = ts. students) // true; // Summary: the method should be written on the prototype to save resources, and the attribute of the reference type should be written in the constructor to avoid pollution; // Constructor question function A () {this. name = 'a';} function B () {this. name = 'B';} var a = new A; console. log (. constructor = A) // true // replace B's prototype object with A's instance object B. prototype = New A; var B = new B; console. log (B. constructor = B) // false console. log (B. constructor = A) // true // indicates that rewriting the prototype object will result in A problem pointed to by the constructor. // The constructor is modified to B. prototype. constructor = B; console. log (B. constructor = B) // true // constructor is mounted on prototype. If prototype is rewritten, the constructor console is automatically rewritten. log (B. isPrototypeOf (B) // false; console. log (Object. getPrototypeOf (B) // A // The contructor cannot change the prototype reference relationship either. // This method also produces the B constructor pointing to A question. Question B. prototype = {//...} // It is recommended to write. prototype. getName = function () {console. log (this. name);} function C () {this. name = 'C';} C. prototype. getAge = function () {console. log ('C age 18')} var c = new c; // only change the Constructor C. prototype. constructor = A; console. log (Object. getPrototypeOf (c) // A console. log (c. isPrototypeOf (C) // falseconsole. log (c. isPrototypeOf (A) // falseconsole. log (c) // C; // c. getName (); // u Ndefinedc. getAge (); // c age 18 // conclusion: as long as the object prototype is changed, its function creation automatically changes. // only changes the point of the constructor, the prototype is inaccurate but not rewritten.

Lab Notes on Constructors and prototypes