Strictly speaking, most of what we learned in the JavaScript section belongs to ECMAScript. ECMAScript, or ES, defines language standards such as the syntax rules for variables, data types, expressions, statements, and functions. Browsers implement most of the ECMAScript specification and extend it with practical features. These extensions are called Web APIs.
JavaScript is a weakly typed, or dynamic, language. You do not need to declare a variable’s type in advance; its type is determined automatically while the program runs.
var age = 10; // Number
var areYouOk = 'yes'; // String
JavaScript has dynamic types, meaning the same variable can be used for different types (its type can change).
var x = 6; // x is a number
var x = "Bill"; // x is a string
Objects are a JavaScript data type. We have already learned about numbers, strings, booleans, and undefined. An object can be understood as a collection of data. It consists of properties and methods.
...Declaring (defining) a complete function involves five parts: the keyword, function name, formal parameters, function body, and return value.
Arrays: An array is a data type that stores data in order.
...Commonly used operators in JavaScript include:
Brendan Eich (born 1961) completed the design of JavaScript in 10 days.
A web page consists of three parts: