Front-end siege lion study NOTE 2: implements a class called man, which contains three methods: ATTR, words, and say.

Interview Questions

This is an interview with Sohu Javascript. The requirements are as follows:

Implement a class called man, which contains three methods: ATTR, words, and say.

 VaR  Man;  //  ++ Answer area ++  //  ++  Try  {  VaR Me = man ({fullname: "Xiaohong" });  VaR She = New MAN ({fullname: "Xiaohong"}); Console. Group (); console.info ( "My name is:" + me. ATTR ("fullname") + "\ n my gender is:" + me. ATTR ("gender" ); Console. groupend ();  /*  ------ [Execution result] ------ my name is: Xiaohong. My gender is: <user has not entered> ------------------  */  Me. ATTR ( "Fullname", "James" ); Me. ATTR ( "Gender", "male" ); Me. fullname = "Waste diesel" ; Me. Gender = "Renshile" ; She. ATTR ( "Gender", "female"); Console. Group (); console.info ( "My name is:" + me. ATTR ("fullname") + "\ n my gender is:" + me. ATTR ("gender" ); Console. groupend ();  /*  ------ [Execution result] ------ my name is: James. My gender is: Male ------------------  */  Console. Group (); console.info ( "My name is:" + She. ATTR ("fullname") + "\ n my gender is:" + She. ATTR ("gender" ); Console. groupend ();  /*  ------ [Execution result] ------ my name is: Xiaohong. My gender is: Female ------------------ */  Me. ATTR ({ "Words-limit": 3 , "Words-emote": "smile" }); Me. Words ( "I like watching videos. " ); Me. Words ( "Our office is so beautiful. " ); Me. Words ( "There are so many beautiful women in the video! " ); Me. Words ( "I usually watch Youku! " ); Console. Group (); console. Log (me. Say ());  /*  ------ [Execution result] ------ James smiled: "I like watching videos. Our office is so beautiful. There are so many beautiful women in the video! "------------------ */  Me. ATTR ({ "Words-limit": 2 , "Words-emote": "Shout" }); Console. Log (me. Say (); console. groupend ();  /*  ------ [Execution result] ------ James shouted: "I like watching videos. Our office is so beautiful. "------------------  */  }  Catch  (E) {console. Error ( "Execution error, error message:" + E );} 

Analysis Process

The analysis is as follows:

From the perspective of instantiating an object, you can use new or not. This is a scope Security constructor. The principle is to check whether this points to the current method, if not, a new object is forced out. The general framework is as follows:

 
Man =Function(OBJ ){If(This InstanceofArguments. callee ){For(VaREInOBJ ){This[E] =OBJ [e] ;}}Else{Return NewMAN (OBJ );}};
 

Through observation, we can find that the ATTR method can get or set the attribute value, and the parameter can be a string, a string plus a value, and an object. The ATTR method is defined as follows:

Man. Prototype. ATTR = Function  (ATTR, Val ){  If  (VAL ){  This [ATTR] = Val ;}  Else  {  If ( Typeof ATTR = "string" ){  Return   This . Hasownproperty (ATTR )?This [ATTR]: "<user not entered>" ;}  Else   If ( Typeof ATTR = "object" ){  For ( VaR E In  ATTR ){  This [E] = ATTR [e] ;}}  Else  {}}} 

By observing words, we can find that some strings are passed in for calling in the say method, so here we directly add an array of words_limit_arr to man to store these strings, therefore, the words method is implemented as follows:

 
Man. Prototype. Words =Function(STR ){This. Words_limit_arr.push (STR );}
 

Finally, we can see through observation that the say method is to add the value of the fullname attribute to the value of limit-emote, plus the strings connected by the previous words-limit words_limit_arr items, so the definition is as follows:

 
Man. Prototype. Say =Function(){Return This["Fullname"] +This["Words-emote"] + ":" + "\" "+This. Words_limit_arr.slice (0,This["Words-limit"]). Join ("") + "\"";}
 

The whole combination is:

VaR Man = Function  (OBJ ){  If ( This   Instanceof  Arguments. callee ){  For ( VaR E In  OBJ ){  This [E] = OBJ [E];}  This . Words_limit_arr =[];}  Else  {  Return   New  MAN (OBJ) ;}}; man. Prototype. ATTR = Function  (ATTR, Val ){  If  (VAL ){  This [ATTR] = Val ;}  Else  {  If (Typeof ATTR = "string" ){  Return   This . Hasownproperty (ATTR )? This [ATTR]: "<user not entered>" ;}  Else   If ( Typeof ATTR = "object" ){  For ( VaR E In ATTR ){  This [E] = ATTR [e] ;}}  Else  {}}} Man. Prototype. Words = Function  (STR ){  This  . Words_limit_arr.push (STR);} Man. Prototype. Say = Function  (){  Return   This ["Fullname"] + This ["Words-emote"] + ":" + "\" "+ This . Words_limit_arr.slice (0, This ["Words-limit"]). Join ("") + "\"" ;} 

However, there is a problem that cannot be solved, that is, the assignment of me. ATTR ("fullname", "XXX") method cannot be changed when the assignment of me. fullname = "XXX") method is used. The running result is as follows:

How can this problem be solved?CodeThe idea of that friend is to let me. ATTR ("fullname", "XXX") assign a value to fullname and me. fullname is not the same attribute.

Before thinking about other solutions, I had to modify my Code as follows:

 VaR Man = Function  (OBJ ){  If ( This  Instanceof  Arguments. callee ){  This . Infos = {  };  For ( VaR E In  OBJ ){  This . Infos [e] = OBJ [E];}  This . Words_limit_arr = [];}  Else {  Return   New  MAN (OBJ) ;}}; man. Prototype. ATTR = Function  (ATTR, Val ){  If  (VAL ){  This . Infos [ATTR] = Val ;}  Else  {  If ( Typeof ATTR = "string"){  Return   This . Infos [ATTR]? This . Infos [ATTR]: "<user not input>" ;}  Else   If ( Typeof ATTR = "object" ){  For ( VaR E In  ATTR ){  This . Infos [e] =ATTR [e] ;}}  Else  {}}} Man. Prototype. Words = Function  (STR ){  This  . Words_limit_arr.push (STR);} Man. Prototype. Say = Function  (){  Return   This . Infos ["fullname"] + This . Infos ["words-emote"] + ":" + "\" "+ This . Words_limit_arr.slice (0,This . Infos ["words-limit"]). Join ("") + "\"" ;} 

After modification, the running effect is as follows:

Summary

This topic mainly examines knowledge points such as scope Security constructor, instanceof/typeof, slice usage, array traversal, and object member traversal.

For the "use me. the value assignment in fullname = "XXX" mode cannot change me. assignment in ATTR ("fullname", "XXX") mode ". If you have any new solutions, please give us some advice. You are also welcome to discuss my solution.