javascript - Why must I use + in mongoDB query -

i doing learnyoumongo tutorials learn mongodb.

on third excercise (the find tutorial) couldn't work until found solution. mistake query needed "+" in front of argument.

so db.coll.find({ $gt: process.argv[2] }) did not work, { $gt: +process.argv[2] } did.

perhaps stupid question, plus sign, , when use it?

also play role in regular javascript?

the + in context implicit cast number. process.argv[2] string. + quick, easy, , safe way cast number. $gt expects number comparison rather string -- numeric string.