babel-debug-tools

Babeljs Debug Tools helps you insert debug code and easely remove it when deploy to production

LOG

Similar to console.log but logs also identifiers and source code position

// app.js
import { H5 } from './debug'
function sum(a,b) {
  H5.LOG(a,b);
  → console.log('a='+ a, 'b='+ b, ' at app.js:3:3');
  return a+b;
}

ASSERT

Similar to assert but logs also identifier and source code position

// app.js
import { H5 } from './debug'
function sum(a,b) {
  H5.ASSERT(a>0,b>0)
  → if (!(a>0)) throw new Error('assert a>0 at app.js:3:3');
  → if (!(b>0)) throw new Error('assert b>0 at app.js:3:3');
  return a+b
}

TRACE

Useful for test local variables on test units. It's not for production mode.

// lib.js
import { H5 } from './debug'
function quadraticEquation(a,b,c) {
  const delta = b*b - 4*a*c; ← b² – 4ac
  H5.TRACE(a, b, c, delta)
  → tracelog.push('a=' +a + ' b=' + b +' c=' + c + ' delta=' + delta);
  if (delta<0) return null
  const x1 = (-b + sqrt(delta)) / (2*a)
  const x2 = (-b - sqrt(delta)) / (2*a)
  return {x1, x2}
}
// test.js
import { H5 } from './debug'
it(()=>{
  H5.RESET() 
  → tracelog = [] // traceLog is a global
  const result = quadraticEquation(1, 8, -9) // x² + 8x - 9 = 0
  const deltaWasTraced = H5.ASSERT(/delta=100/} 
  → const deltaWasTraced = traceLog.some(l=>/delta=100/.test(l)))
  except(deltaWasTraced).toBe(true)
  except(H5.HISTORY()).toBe('a=1 b=8 c=-9 delta=100')
  ...
})

Install

Using npm:

npm install --save-dev babel-debug-tools

Setup

babel.config.js:

module.exports = {
  plugins: [
      [
        require.resolve('babel-plugin-debug-tools'),
        {
          mode: 'development',
          identifier: 'H5'
        }
      ]
    ]
  ]
}

mode

Define plugin transform mode

• development or test - activate tools, this is default mode.
• production - remove debug tools from output

identifier

name of identifier for use with debug tools, default is H5

debug.js module

You will need a debug module, like that but customized to your needs.

See sample project or DEBUG.ts

let traceLog = [];

export const H5 = {
  LOG() {
    console.log(formatArgs(arguments, 1));
  },
  ASSERT() {
    const loc = arguments[0]
    for (let i = 1; i < arguments.length; i++) {
      const arg = arguments[i]
      if (Array.isArray(arg)) {
        if (!arg[1]) throw new Error(
          'ASSERT FAIL: ' + arg[0] + ' at ' + formatLoc(loc) +
          (arg[2] ? JSON.stringify(arg[2]) : '')
        );
      } else {
        if (!traceLog.some(l => arg.test(l)))
          throw new Error('NOT FOUND IN HISTORY: ' + arg.toString() + ' at ' + formatLoc(loc))
      }
    }
  },
  RESET() {
    traceLog = [];
  },
  HISTORY() {
    return traceLog.join('\n')
  },
  TRACE() {
    traceLog.push(formatArgs(arguments, 0));
  },
  CHECK(regExp) {
    return traceLog.some(l => regExp.test(l))
  }
};

function formatLoc(loc) {
  return (loc.filename || '') + ':' + loc.line + ':' + loc.column + ' ';
}
function formatArg(arg) {
  if (typeof arg === 'string') return arg
  return JSON.stringify(arg)
}
function formatArgs(args, sLoc) {
  const flatArgs = []
  for (let i = 0; i < args.length - sLoc; i++) {
    const arg = args[i]
    if (Array.isArray(arg) && arg.length == 2) {
      flatArgs.push(formatArg(arg[0]) + ': ' + formatArg(arg[1]))
    }
    else flatArgs.push(formatArg(arg))
  }
  if (sLoc)
    flatArgs.push(formatArg(formatLoc(args[args.length - 1])))
  return flatArgs.join(' ')
}