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About the difference between substring() and substr() (detailed tutorial)

亚连
亚连Original
2018-06-14 16:36:081424browse

Below I will share with you an example based on the use and difference between substring() and substr(). It has a good reference value and I hope it will be helpful to everyone.

In JavaScript, interception is usually used. The so-called interception is actually to obtain the content from a certain position to a certain position of the intercepted element. Then JS provides me with the two substring and substr Method:

What is the difference between these two interception methods? Direct code demonstration:

substring(a,b):

a: indicates the starting position

b: Indicates the end position

! But it is worth noting: when intercepting, the intercepted content includes the element at the starting position, but does not include the element at the ending position!

Example:

function sub1(){
  var str = 'javascript';
  return str.substring(0,4);
 }
 console.log(sub1());  //返回值为‘java'
 
 function sub2(){
  var str = 'javascript';
  return str.substring(1,4);
 }
 console.log(sub2());  //返回值为‘ava'

Summary: When substring is intercepted, the starting position is included and the ending position is not included, and Both parameters a and b are positional values, that is, index values ​​

substr (index, length):

index: Represents the starting position

length: Represents the length of the intercepted content

! The element at the starting position is included when intercepting!

Example:

function sub3(){
  var str = 'javascript';
  return str.substr(0,4);
 }
 console.log(sub3());   //返回值为‘java'
 
 function sub4(){
  var str = 'javascript';
  return str.substr(1,4);
 }
 console.log(sub4());  //返回值为‘avas'

Summary: When substr is intercepted, including the starting position, the two parameters are starting Starting position and interception length

! Pay attention to the distinction and use it wisely!

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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