javascript-gotchas-key.js

[100, 10, 5, 1].sort() // -> [1, 10, 100, 5]

parseInt(0.0000007) // -> 7
parseInt('0.0000007') === parseInt('1e-7'); // -> false

[1, 2, 3, 4, 5].map(parseInt) // -> [1, NaN, NaN, NaN, NaN]

x = null
typeof x === 'object' // -> true

new String('abc') === String('abc') // -> false
new String('abc') === 'abc' // -> false

if (new Boolean(false)) {
  console.log('The universe has imploded');
} else {
  console.log('Everything is fine (for now)')
} // -> The universe has imploded

var pentagram = '⛤';
pentagram.length // -> 1
var smile = '😀';
smile.length // -> 2

var array = new Array(10);
array[7] = 'foo';
console.log(array.map(function () { return 'bar'; })); // -> [ , , , , , , , 'bar', ,  ]

[] + [] // -> ''
{} + {} // -> '[object Object][object Object]'
[] + {} // -> '[object Object]'
{} + [] // -> 0
'' * 11 // -> 0

null == undefined // -> true
null === undefined // -> false
void 0 // -> undefined

Math.pow(NaN, 0) // -> 1
Math.pow({}, []) // -> 1

typeof [1, 2, 3] // -> 'object'

'10' + '7' // -> '107'
'10' - '7' // -> 3
'10' * '7' // -> 70

{ 0.0000001: true, '1e-7': false } // -> { '1e-7': false }

var r = /a/g; console.log(r.test("abc"), r.test("abc")); // true false