Making is thinking.

THE TROUBLED PROGRAMMER

In JavaScript we can apply double negation to check if an object exists, which isn’t inelegant.

TO CHECK IF a thing is a thing I used to write something like this:

function has (obj, key) {
  return obj[key] ? true : false
}

Recently I realized the obvious; we can combine two logical NOTs to check for not undefined and not null:

var tap = require('tap')
 
function has (obj, key) {
  return !!obj[key]
}
 
tap.test('has', function (t) {
  t.notOk(has({}, 'cash'), 'should be false')
  t.notOk(has({ cash: undefined }, 'cash'), 'should be false')
  t.notOk(has({ cash: null }, 'cash'), 'should be false')
  t.ok(has({ cash: 100 }, 'cash'), 'should be true')
  t.end()
})

You don’t know what you don’t know.