The code is as follows ：
function Foo(){
getName = function(){ console.log("1"); }
return this;
}
Foo.getName = function(){
console.log("2");
}
Foo.prototype.getName = function(){
console.log("3");
}
var getName = function(){
console.log("4");
}
function getName(){
console.log("5");
}
Foo.getName(); //
getName(); //
Foo().getName(); //
getName(); //
new Foo.getName(); //2 => new (Foo.getName)() new No parameter list
new Foo().getName(); // 3 => (new Foo()).getName(); //new With parameter list
new new Foo().getName(); //3 => new ((new Foo()).getName)() //new With parameter list
Foo.getName()
The output is :2
principle ： What he's calling is Foo Static method of （ If C#、java And so on ）, Because Javascript Medium Function Itself is Function and Object The combination of , therefore function It's a function , Also object . ad locum Foo It's the execution of one of his objects function nothing more .
getName()
The output is ：4
principle ： Maybe you wonder why not 5,function The variable is raised to the top of the scope , and var Defined will not , therefore var The statement's override function Statement . So the result is 4
Foo().getName()
The output is ：1
principle ：Foo() It's a function call ,Foo In the executor getName Reassigned （ Overall getName, Look up... Based on the scope chain ）, Back to this by window(Foo There is no call to , The default is global ), then .getName() Called the global getName（ It means being Foo I wrote getName）, So the result is :1
getName()
The output is ：1 principle ： because Foo In the executor, the global getName Rewrote , At this time, the call is global getName. So the result is :1
new Foo.getName()
The output is ：2
principle ：
- because new No arguments , And new The operation optimization level with parameters is the same .new There is participation in . Operators at the same level , and new A lower level of nonparametric . So it's going to execute first . Operator to Foo Static method of getName
- And then execute new, What you get is Foo.getName An example of . So the output is ：2
new Foo().getName()
The output is ：3
principle ：
- because new It's involved , And . Operator siblings , In order of execution from left to right , Execute first new Foo().
- new Foo() It needs our attention , Because he has a return value . There are two types of return values ：
- No return has the same effect as return as a basic type ： Return all instance objects （ It's the current this）
- Return to reference type ： The object returned is of this reference type , The instance object is replaced （ It's the current this No return ）. Factor new Foo() The return is the instance object
- .getName()： Select this method for the previous instance , So the output is ：3
new new Foo().getName()
The output is ：3
principle ： Mainly is the operator priority examination , It should not be directly used in case development . First new Ginseng , then .getName(. Operator )（ Why . Operator , This is because new The level of no parameter is one grade lower ）, Again new Ginseng .
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