内部函数无法访问外部函数变量

Question

I have created the following jsfiddle which highlights my problem. http://jsfiddle.net/UTG7U/

var ExampleObject = function() {
   var myArray = new Array();
   this.example = function() {
       alert(this.myArray);
   };
}

var exampleObj = new ExampleObject();
exampleObj.example();​

I am new to JavaScript and trying to create an object, field and a method. I can't get my method to access my field variable.

Answer 1

you were trying to access a local variable using this operator which is wrong, so here is the working example

var ExampleObject = function() {
   var myArray = new Array(1,2,3);
   this.example = function() {
       alert(myArray);
   };
}
var exampleObj = new ExampleObject();
exampleObj.example();​

Link: http://jsfiddle.net/3QN37/

Answer 2

You have confused two types of variables: Local variables and member variables. var myArray is a local variable. this.myArray is a member variable.

Solution using only local variables:

var ExampleObject = function() {
   var myArray = new Array(); // create a local variable
   this.example = function() {
       alert(myArray); // access it as a local variable
   };
}

var exampleObj = new ExampleObject();
exampleObj.example();​

Solution using only member variables:

var ExampleObject = function() {
   this.myArray = new Array(); // create a member variable
   this.example = function() {
       alert(this.myArray); // access it as a member variable
   };
}

var exampleObj = new ExampleObject();
exampleObj.example();​

Answer 3

You don't need the this.myArray . Using myArray alone will suffice (and work).

Answer 4

alert(myArray); should work fine I think

Answer 5

What this is changes with the scope of each function. However, myArray will be visible to inner function. Example:

var ExampleObject = function() {
   var myArray = new Array();
   this.example = function() {
       alert(myArray);
   };
}
var exampleObj = new ExampleObject();
exampleObj.example();​