Exceptional circumstances: preventing programmer failure at runtime

node-add.js

var assert = require('assert')

function add(a, b) {
  assert(typeof a === 'number', 'a is not a number got ' + typeof a)
  assert(typeof b === 'number', 'b is not a number got ' + typeof b)
  return a + b
}

add(1, 2)

add('1', 2)#! node node-add.js 

/* logs:
 
AssertionError: a is not a number got string
    at add (/Users/brianleroux/Repo/33ed82ee20aa0f4b11d630a9d423b2df/node-add.js:4:3)
    at Object.<anonymous> (/Users/brianleroux/Repo/33ed82ee20aa0f4b11d630a9d423b2df/node-add.js:11:1)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:134:18)
    at node.js:962:3
*/