bjf-flatiron / fewpjs-js-fundamentals-calling-methods

JavaScript Fundamentals: Calling Methods

Learning Goals

• Define a JavaScript method

Introduction

In the previous lessons, we did a very important thing in the JavaScript language, we called a method. We glossed over some of the detail about what was happening at the technical level at that time. Let's put some new vocabulary around what we did.

Define a JavaScript Method

Let's consider the document.querySelector method.

This code calls the method querySelector. The method is said to be "defined in" the object document.

Calling is the same as running. We do that when we write:

document.querySelector(); // Notice the addition of ()

When we call document.querySelector(), we provide it an argument, a bit of text, a String of text that goes inside the ().

The method document.querySelector() expects us to provide a CSS identifier that will help us find the node we want as an argument.

If the document object finds an HTMLElement in its representation of the page, it returns it. Otherwise the method returns null.

The thing document.querySelector() returns is also an object. It, too, has both information and methods, state and behavior, properties and methods (they all mean the same thing). This HTMLElement instance has methods like remove().

Conclusion

JavaScript methods are actions that can be performed on objects. Objects have many useful methods that help us modify and iterate through them, for example. The DOM selection method document.querySelector() is a powerful tool for finding elements needed to make updates and changes to the DOM using methods like remove().

Resources

JavaScript Object Methods