doc: update question 467 substr vs substring

Author: mauroaccornero

README.md

@@ -8845,8 +8845,29 @@ The execution context is created when a function is called. The function's code
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 467. ### What is the difference between substring and substr methods?
- Both substring() and substr() are string methods, which are used to find substring of a given string. But there are some notable differences with their usage,
- 
+There are subtle differences between the substring() and substr() methods, so you should be careful not to get them confused.
+
+- The two parameters of substr() are start and length, while for substring(), they are start and end.
+- substr()'s start index will wrap to the end of the string if it is negative, while substring() will clamp it to 0.
+- Negative lengths in substr() are treated as zero, while substring() will swap the two indexes if end is less than start.
+
+Furthermore, substr() is considered a legacy feature in ECMAScript, so it is best to avoid using it if possible.
+
+```javascript
+const text = "Mozilla";
+console.log(text.substring(2, 5)); // "zil"
+console.log(text.substr(2, 3)); // "zil"
+```
+
+sources: 
+- [substring mdn web docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring#the_difference_between_substring_and_substr)
+- [substr mdn web docs (deprecated)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr)
+- [substr current ecmascript specification](https://262.ecma-international.org/14.0/index.html?_gl=1*1bpcj45*_ga*NDgyMjM0MDA0LjE3MjY2MDQ1OTM.*_ga_TDCK4DWEPP*MTcyNjYwNDU5My4xLjEuMTcyNjYwNDc0OS4wLjAuMA..#sec-string.prototype.substr)
+- [substr draft ecmascript specification](https://tc39.es/ecma262/#sec-string.prototype.substr)
+- [substring current ecmascript specification](https://262.ecma-international.org/14.0/index.html?_gl=1*1bpcj45*_ga*NDgyMjM0MDA0LjE3MjY2MDQ1OTM.*_ga_TDCK4DWEPP*MTcyNjYwNDU5My4xLjEuMTcyNjYwNDc0OS4wLjAuMA..#sec-string.prototype.substring)
+- [substring draft ecmascript specification](https://tc39.es/ecma262/#sec-string.prototype.substring)
+- [substr caniuse](https://caniuse.com/mdn-javascript_builtins_string_substr)
+- [substring caniuse](https://caniuse.com/mdn-javascript_builtins_string_substring)
 
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