showandtell/examples/custom-command.js

A Javascript library providing debugger-like command-line interactivity for program state inspection and modification

'use strict'

/**
 * This example shows how to create a new command and register it
 * to a story.  When run, you will be able to do things like
 *
 * help square
 * square test
 */

const showandtell = require('showandtell')

const square = new showandtell.Command({
  name: 'SQUARE',
  help: 'SQUARE <variable>',
  args: [{name: 'variable', help: 'The name of a top-level value to compute the square of'}],
  func: function (state, args, next) {
    if (!state.hasOwnProperty(args.variable)) {
      next(new Error(`State does not have top-level key ${args.variable}`), state)
    } else {
      state[args.variable] *= state[args.variable]
      next(null, state)
    }
  }
})

const story = new showandtell.Story([square])
let state = {test: 32}

story.start(state)
.then((newState) => {
  console.log('new test value: ', state.test)
})
.catch(console.error)