What is the difference between substring and substr methods?

Both substring and substr are used to extract parts of a string, but there are subtle differences between the substring() and substr() methods in terms of syntax and behavior.

1. substring(start, end)

• Parameters:
• start: The index to start extracting (inclusive).
• end: The index to stop extracting (exclusive).
• Behavior:
• If start > end, it swaps the arguments.
• Negative values are treated as 0.

          let str = "Hello World";
          console.log(str.substring(0, 5));   // "Hello"
          console.log(str.substring(5, 0));   // "Hello" (swapped)
          console.log(str.substring(-3, 4));  // "Hell" (negative = 0)
         

1. substr(start, length) _(Deprecated)_

• Parameters:
• start: The index to start extracting.
• length: The number of characters to extract.
• Behavior:
• If start is negative, it counts from the end of the string.
• If length is omitted, it extracts to the end of the string.

         let str = "Hello World"; console.log(str.substr(0, 5)); // "Hello" 
         console.log(str.substr(-5, 3)); // "Wor" (starts from 'W')`
         

Note: substr() is considered a legacy feature in ECMAScript, so it is best to avoid using it if possible.