Judge whether the beginning and end of the string contain target parameters: startswith() and endswith() methods

startsWith()： Indicates whether the parameter string is in the of the original string Head , return Boolean value

endsWith()： Indicates whether the parameter string is in the of the original string The tail , return Boolean value

application ：

 let str = 'wo?e'
      console.log(str.endsWith());   // false

      console.log(str.startsWith('w')) //true
      console.log(str.startsWith('')) //true
      console.log(str.endsWith('')) //true
      console.log(str.endsWith('e')) //true

      console.log(str.endsWith('?', 3));   // true

From the example we can see ：

1、 When a string calls endsWith() When the method does not pass parameters , The default is undefined The result is false;

2、 When looking for an empty string , The result is true, That's because empty characters exist in any string ;

3、 When there is a second parameter , The second parameter is the length of the string , The second parameter will take the specified length of the original string as the target string .