Javascript String substr()

Introduction

Javascript String substr() gets a sub string from a longer string.

The substr() method can accept one or two arguments. 

str.substr(start[, length])
  • start - the index of the first character to include.
  • length - Optional. The number of characters to extract.

If the second argument is omitted, it is assumed that the ending position is the length of the string.

The substr() method does not alter the string itself.

It returns a string value as the result, leaving the original unchanged. 

let stringValue = "hello world"; 
console.log(stringValue.substr(3));       // "lo world" 
console.log(stringValue.substr(3, 7));    // "lo worl"

For the substr() method, a negative first argument is treated as the length of the string plus the number, whereas a negative second number is converted to 0. 

let stringValue = "hello world"; 
console.log(stringValue.substr(-3));        // "rld" 
console.log(stringValue.substr(3, -4));     // "" (empty string)



PreviousNext

Related