Check substring

Write a JavaScript function to check whether a string contains 'code' string, return true if it contains 'code' string or return false otherwise.

Sample Code:

def checkString(str, search):
# Enter your logic here...

Examples:

Input: 'Codetisan', 'code'
Output: true
Explanation: 'Codetisan' string contains 'code' string, therefore it should return true.

Input: 'source code', 'CODE'
Output: true
Explanation: 'source code' string contains 'code' string, therefore it should return true.

Input: 'Developer', 'code'
Output: false
Explanation: 'Developer' string does not contain 'code' string, therefore it should return false.