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/* VT100 terminal reset (<ESC>c) */
console.log('\033c');
/* numbers comparations */
> '2' == 2
true
> '2' === 2
false
> [2] == 2
true
> [] + []
''
> [] == []
false
> typeof []
'object'
> [] == ![]
true
> +[] == +![]
true
/* null comparation */
> 0 > null
false
> 0 >= null
true
> 0 == null
false
> 0 <= null
true
> 0 < null
false
> typeof null
'object'
> null instanceof Object
false
/* checking array type */
> {}.toString.call([])
'[object Array]'
> function FooBar() {}
undefined
> {}.toString.call(new FooBar)
'[object Object]'
> (new FooBar).constructor == Foo
false
> [] instanceof Array
true
> Array.isArray([])
true
/* math */
> 999999999999999
999999999999999
> 9999999999999999
10000000000000000
> -9999999999999999
-10000000000000000
> 0.1 + 0.2 == 0.3
false
> 0.1 + 0.2
0.30000000000000004
> 3 > 2 > 1
false
> 3 > 2 >= 1
true
> '2' + 1
'21'
> '2' - 1
1
> '2' - -1
3
> 1/0
Infinity
> typeof Infinity
'number'
> 0 === -0
true
> 1/0
Infinity
> 1/-0
-Infinity
> Infinity == -Infinity
false
Number.MAX_VALUE
1.7976931348623157e+308
> 0 - 1
-1
> Number.MIN_VALUE < 0
false
> Number.MIN_VALUE
5e-324>
> Math.max(1,2,3)
3
> Math.min(1,2,3)
1
> Math.max() > Math.min()
false
> Math.max()
-Infinity
> Math.min()
Infinity
/* string */
> 'wtf' instanceof String
false
> typeof 'wtf'
'string'
> typeof String('wtf')
'string'
> String('wtf') === 'wtf'
true
> String('wtf') === new String('wtf')
false
> String('wtf') == new String('wtf')
true
> new String('wtf')
{ '0': 'w',
'1': 't',
'2': 'f' }
> new String('wtf').toString()
'wtf'
> 'wft' + 1
'wft1'
> 'wft' - 1
NaN
/* NaN */
> typeof NaN
'number'
> typeof 1138
'number'
> 1138 == 1138
true
> NaN == NaN
false
> isNaN('wft' - 1)
true
/* boolean math */
> true + false
1
> true + true == true
false
/* construct function */
> new 0xff.constructor.constructor('console.error("WTF")')()
WTF
> new Function('console.error("WTF")')()
WTF
/* typeof/instanceof */
> Array instanceof Array
false
> new Array instanceof Array
true
> Math instanceof Math
TypeError: Expecting a function in instanceof check, but got #<Object>
at repl:1:18
at REPLServer.self.eval (repl.js:110:21)
at Interface.<anonymous> (repl.js:239:12)
at Interface.emit (events.js:95:17)
at Interface._onLine (readline.js:203:10)
at Interface._line (readline.js:532:8)
at Interface._ttyWrite (readline.js:761:14)
at ReadStream.onkeypress (readline.js:100:10)
at ReadStream.emit (events.js:98:17)
at emitKey (readline.js:1096:12)
>

garrows commented Jan 24, 2017

['a','b','c'][3,2,1] === 'b'

fletom commented Feb 8, 2017

> [10, 9, 8, 3, 2, 1, 0].sort()
[ 0, 1, 10, 2, 3, 8, 9 ]
> '1' / '1'
1
> '1' * '1'
1
> '1' + '1'
'11'

Mechazawa commented May 24, 2017 edited

>[1,2,3,4].map(foo => {bar: foo * 10})
[undefined, undefined, undefined, undefined]
>[1,2,3,4].map(foo => {bar: foo * 10, baz: foo})
Syntax error!
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