Let’s learn JS! Reading the “JS Good Parts book”

I’ve decided to start learning Javascript because I want understand how it works.

Let’s start with Functions:

Function invocation:

In addition to the declared parameters, every function receives two additional parameters: this and arguments. The this parameter is very important in object oriented programming, and its value is determined by the invocation pattern. There are four patterns of invocation in JavaScript: the method invocation pattern, the function invocation pattern, the constructor invocation pattern, and the apply invocation pattern. The patterns differ in how the bonus parameter this is initialized.

Note: if too many or too little parameters passed to function they will be ignored or set to undefined. There is no type checking. Also this will not throw any runtime errors.

1.Method invocation pattern

// Create myObject. It has a value and an increment
// method. The increment method takes an optional
// parameter. If the argument is not a number, then 1
// is used as the default.
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

2. Function invocation pattern

 

3. Constructor invocation pattern

 

4. Apply invocation pattern

 

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