方法调用模式

Question

var myObject = {
    value: 0,
    increment: function (inc) {
        this.value += typeof inc === 'number' ? inc : 1;
    }
};


myObject.increment( );
document.writeln(myObject.value); //1

myObject.increment(2);
document.writeln(myObject.value); //3

I can understand this function.

But I have trouble to understand why result of second call is 3? Because in my mind that result should be 2.

In my head process is looking like this:

var myObject = {
    value:0,
    increment: function(2){
        0 += 2;}
};

And result in my opinion should be 2, but what is reason to be 3 instand.

Answer 1

Please think it as single json

 var myObject = {
         value: 0,
         increment: function (inc) {
             this.value += typeof inc === 'number' ? inc : 1;
} };

Then you called

myObject.increment( );
 document.writeln(myObject.value); //1

Which updated object as

 var myObject = {
         value: 1,
         increment: function (inc) {
             this.value += typeof inc === 'number' ? inc : 1;
} };

Now you call this

myObject.increment(2);
document.writeln(myObject.value); //3

so now it will 3 as expected