Question

The alert function can be useful as an output device when experimenting, but clicking away all those little windows will get on your nerves. In past examples, we’ve used console.log to output values. Most JavaScript systems (including all modern web browsers and Node.js) provide a console.log function that writes out its arguments to some text output device. In browsers, the output lands in the JavaScript console. This part of the browser interface is hidden by default, but most browsers open it when you press F12 or, on Mac, when you press Command-Option-I. If that does not work, search through the menus for an item named “web console” or “developer tools”.

var x = 30;
console.log("the value of x is", x);
// → the value of x is 30

Though variable names cannot contain period characters, console.log clearly has one. This is because console.log isn’t a simple variable. It is actually an expression that retrieves the log property from the value held by the console variable. We will find out exactly what this means in Chapter 4 .

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.