Coffeescript - Finding substring with "in" -

in coffeescript following gives true

"s" in "asd" # true 

but gives false

"as" in "asd" # false 

• why this?
• it happens strings more 1 character?
• is in not suited task?

x in y syntax coffeescript expects y array, or array object. given string, convert array of characters (not directly, iterate on string's indexes if array).

so use of in:

"as" in "asd" # => false 

is equivalent

"as" in ["a","s","d"] # => false 

this way easier see why returns false.

the little book of coffeescript has on in:

includes

checking see if value inside array typically done indexof(), rather mind-bogglingly still requires shim, internet explorer hasn't implemented it.

var included = (array.indexof("test") != -1) 

coffeescript has neat alternative pythonists may recognize, namely in.

included = "test" in array 

behind scenes, coffeescript using array.prototype.indexof(), , shimming if necessary, detect if value inside array. unfortunately means same in syntax won't work strings. need revert using indexof() , testing if result negative:

included = "a long test string".indexof("test") isnt -1 

or better, hijack bitwise operator don't have -1 comparison.

 string   = "a long test string"  included = !!~ string.indexof "test" 

personally, bitwise hack isn't legible, , should avoided.

i write check either indexof:

"asd".indexof("as") != -1 # => true 

or regex match:

/as/.test "asd" # => true 

or if using es6, use string#includes()