Is there a way to read standard input with JavaScript?

It's not in the ECMAScript (standardized version of JavaScript) standard library. However, some implementations of JavaScript do include it. For example, CommonJS, which is used by several out-of-the-browser JavaScript environments, has a system.stdin property. Rhino can use Java's standard input classes.

If you're just trying to practice programming, you can use a textarea as a substitute for standard input.

If you use node to act as an interpreter in the terminal, you can use this:

---- name.js ----
var readline = require('readline');

var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout

});

rl.question(">>What's your name?  ", function(answer) {
   console.log("Hello " + answer);
   rl.close();
});

----- terminal ----
node name.js

Use just readline()

var a = readline();

the value which you give input will be stored in variable a.

readline() : Reads a single line of input from stdin, returning it to the caller. You can use this to create interactive shell programs in JavaScript.

It depends on the environment that your JavaScript is executing in.

In the browser, there is no standard input (the browser isn't a console). The input would come generally from some textbox element in a form on the page.

If you're using something like Rhino, then you can import the standard Java I/O classes and read from stdin that way.