JavaScript types

A quiz about JavaScript types and their conversion.

Select the correct evaluation result

	true	false
0 == false	[x]	[ ]
0 === false	[ ]	[x]
1 == true	[x]	[ ]
'1' == false	[ ]	[x]

Get it right!

Choose the returned value for each typeof operator use cases. For example the first one would be executed as typeof "Hello" and would return a "string".

typeof ...	"object"	"number"	"array"	"string"	"function"	"undefined"	"boolean"
"Hello"	[ ]	[ ]	[ ]	[x]	[ ]	[ ]	[ ]
true	[ ]	[ ]	[ ]	[ ]	[ ]	[ ]	[x]
108	[ ]	[x]	[ ]	[ ]	[ ]	[ ]	[ ]
[0, 1, 2]	[x]	[ ]	[ ]	[ ]	[ ]	[ ]	[ ]
{}	[x]	[ ]	[ ]	[ ]	[ ]	[ ]	[ ]
new Date()	[x]	[ ]	[ ]	[ ]	[ ]	[ ]	[ ]
undefined	[ ]	[ ]	[ ]	[ ]	[ ]	[x]	[ ]
"true"	[ ]	[ ]	[ ]	[x]	[ ]	[ ]	[ ]
12.8	[ ]	[x]	[ ]	[ ]	[ ]	[ ]	[ ]
alert	[ ]	[ ]	[ ]	[ ]	[x]	[ ]	[ ]

How about trying it in the console of your browser?

What are the output values of the following expressions?

1 + 2

• 12

• 3

"1" + 2

• 12

• "12"

• 3

• "3"

+"1" + 2

• 12

• "12"

• 3

• "3"

1 + "2"

• 12

• "12"

• 3

• "3"

1+ +"2"

• 12

• "12"

• 3

• "3"

String always wins! ...unless it is turned to a number first.