How to use LIKE operator in mongodb?

LIKE operator in other relational database is mostly used to match patterns. This operator can be used with wildcard operators like modulo(%) and underscore(_). The modulo sign represents zero or more characters/numbers whereas the underscore represents exactly one character/number.

SELECT * FROM customers WHERE customerName LIKE '%mas'   //Anything that end with 'mas'   e.g Tomas
SELECT * FROM customers WHERE customerName LIKE '%nal%'  //Anthing that contains 'nal' in the middle e.g Ronaldo
SELECT * FROM customers WHERE customerName LIKE '_omas'  //This expects just one character e.g Tomas

In MongoDB, We can achieve  similar way in a different syntax, either by using regex or other simpler ones.

db.customers.find({customerName: /mas$/})   
db.customers.find({customerName: {'$regex': 'mas$', '$options': 'i'}})
##Anything that end with 'mas'   e.g Tomas 
db.customers.find({customerName: /^mas/})  
db.customers.find({customerName: {'$regex': '^mas', '$options': 'i'}}) 
##Anything that starts with 'mas'   e.g Mason 
db.customers.find({customerName: /nal/})   
db.customers.find({customerName: {'$regex': 'nal', '$options': 'i'}}) 
##Anthing that contains 'nal' in the middle e.g Ronaldo