使用关键字“this”有什么好处？

Question

The following code:

var cody = {
  living:true,
  age:23,
  gender:'male',
  getGender:function(){return cody.gender;} 
};

is the same as :

var cody = {
  living:true,
  age:23,
  gender:'male',
  getGender:function(){return this.gender;} 
};

Both codes acheive the same target. The only difference is the swap of cody with the keyword this . What is the benefits of using the keyword this in Javascript? Does it boost the performance? can we ignore it in OOP?

Answer 1

this refers to the current instantiation of the structure in question. For example, the following will fail:

var cody = {
  living:true,
  age:23,
  gender:'male',
  getGender:function(){return cody.gender}
};
var codyCopy = cody;
cody = "foobar";
//undefined
alert(codyCopy.getGender());

However, using this will not, because it correctly refers to the codyCopy :

var cody = {
  living:true,
  age:23,
  gender:'male',
  getGender:function(){return this.gender}
};
var codyCopy = cody;
cody = "foobar";
//male
alert(codyCopy.getGender());

Answer 2

The 'this' keyword is used to refer to the current execution context or object your code is in. It is useful when you want to define a type of object aka a class for example people:

var Person = function(name, living, age, gender) {
    this.name = name;
    this.living = living;
    this.age = age;
    this.gender = gender;
    this.getGender = function(){return this.gender};
};

var cody = new Person('Cody', true, 23, 'male');
var john = new Person('John', true, 25, 'male');

This allows you to use the 'new' keyword to create multiple unique instances of Person with their own values. So on the line var cody = new Person('Cody', true, 23, 'male'); 'this' refers to the cody var and on the next line it refers to the john var. In your code 'this' refers to your cody var because it is inside the cody object but it is not necessary because you aren't creating new codys with there own values.