es6 includes extension of string (), startsWith (), endsWith ()

  Source: "ES 6 Standard Getting Started" (2nd edition) - Ruan Yifeng the ---- Chapter 4 Expansion of the string

Traditionally, JavaScript only indexOfmethod that can be used to determine whether a string is contained in another string. ES6 also provides three new methods.

• Includes () : returns a Boolean value that indicates whether to find a parameter string.
• startsWith () : returns a Boolean value indicating whether the parameter string at the head of the original string.
• endsWith () : returns a Boolean value indicating whether the parameter string at the end of the original string.

let s = 'Hello world!';

s.startsWith('Hello') // true
s.endsWith('!') // true
s.includes('o') // true

 

 These three methods are supported by the second argument indicates the position to start the search.

let s = 'Hello world!';

s.startsWith('world', 6) // true
s.endsWith('Hello', 5) // true
s.includes('Hello', 6) // false

The above codes indicate that the second parameter n, the endsWithbehavior of the other two methods are different. It is for the previous ncharacters, while the other two methods for from the first nposition until the end of the string.