I have the following code however am getting the error Uncaught TypeError: Object #<addThis> has no method 'returnValue' (anonymous function)
function addThis() {
this.value1 = 1;
this.value2 = 2;
var returnValue = function () {
return (this.value1 + this.value2);
}
}
//Instantiate object and write response
var simpleObject = new addThis();
document.write(simpleObject.returnValue());
Because returnValue is just a local variable in the addThis function, it doesn't end up in the object that is created.
Assign the function to a property of the object:
function addThis() {
this.value1 = 1;
this.value2 = 2;
this.returnValue = function() {
return this.value1 + this.value2;
};
}
Or use the prototype for the object:
function addThis() {
this.value1 = 1;
this.value2 = 2;
}
addThis.prototype.returnValue = function() {
return this.value1 + this.value2;
};
this keyword when assigning returnValue as a property of the addThis object? Can I not just have returnValue = ....? If no, why is that?
this.propertyName or someVariable.propertyName. The scope is never inside the object like in an object oriented language. If you use var returnValue = ... it is a local variable, and if you use just returnValue = ... then it becomes a global variable (unless you have var returnValue; anywhere else in the function).when you use this. it is public in scope. when you use var, it is private. since you used var returnValue, it is private, and thus not exposed for use.
In fact, i'm guessing you wanted to hide the values and expose the getter, so reverse what you did..
function addThis() {
var value1 = 1;
var value2 = 2;
this.returnValue = function () {
return (this.value1 + this.value2);
}
}
public scope also mean global scope? I thought this was limited to the object in question as opposed to being in the public scope?.
this in the global namespace of window?var will declare a variable local to the function. I think you meant to assign it to this.returnValue:
function addThis() {
this.value1 = 1;
this.value2 = 2;
this.returnValue = function () {
return (this.value1 + this.value2);
};
}
// Instantiate object and write response
var simpleObject = new addThis();
document.write(simpleObject.returnValue());