Difference between Substr and substring in javascript

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<<–2/”>a href=”https://exam.pscnotes.com/5653-2/”>p>nuances of substr and substring in JavaScript.

Introduction

In JavaScript, substr and substring are string methods used to extract a portion of a string. While both serve a similar purpose, there are subtle yet crucial differences in their behavior and parameters. Understanding these distinctions is vital for writing precise and bug-free JavaScript code.

Key Differences: substr vs. substring

Feature substr() substring()
Parameters start (required), length (optional) start (required), end (optional)
Behavior Extracts a substring of a specified length from the given starting index. Extracts characters from the given starting index up to, but not including, the ending index.
Start Index Negative values count from the end of the string. Negative values are treated as 0.
Length/End Index If omitted, extracts to the end of the string. Negative values are treated as 0. If omitted, extracts to the end of the string.

Illustrative Examples

let str = "Hello, world!";

console.log(str.substr(7, 5));  // Output: "world"
console.log(str.substring(7, 12)); // Output: "world"

console.log(str.substr(-6));   // Output: "world!"
console.log(str.substring(-6));  // Output: "Hello, world!"

Advantages and Disadvantages

Method Advantages Disadvantages
substr() More intuitive if you want to extract a substring of a specific length. Can lead to unexpected results if the length parameter is negative.
substring() Easier to understand when working with indices and extracting characters up to a point. Less intuitive if you need to extract a substring of a specific length.

Similarities

  • Both methods return a new string without modifying the original string.
  • If the start parameter is greater than or equal to the length of the string, both methods return an empty string.

FAQs

Q: Which method is preferred?

A: substring() is generally recommended over substr(). This is because substr() has been marked as legacy in newer JavaScript versions. Additionally, substring()‘s behavior with negative indices is more predictable.

Q: When should I use substr()?

A: If you explicitly need to extract a substring of a known length and the start index is always positive, substr() might be slightly more convenient to use.

Q: Are there alternative methods?

A: Yes, the slice() method offers similar functionality to both substr() and substring(). It’s a versatile option to consider.

Q: Is substr() deprecated?

A: While not officially deprecated, substr() is marked as legacy, implying it might be phased out in future versions of JavaScript.

Let me know if you have any more questions or would like me to elaborate on specific aspects!

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