Rename js snippets

snippets/js/s/replace-last-occurrence.md

@@ -0,0 +1,39 @@
+---
+title: Replace last occurrence in string
+type: snippet
+language: javascript
+tags: [string,regexp]
+author: chalarangelo
+cover: waves
+dateModified: 2021-04-22T09:01:22+03:00
+---
+
+Replaces the last occurrence of a pattern in a string.
+
+- Use `typeof` to determine if `pattern` is a string or a regular expression.
+- If the `pattern` is a string, use it as the `match`.
+- Otherwise, use the `RegExp` constructor to create a new regular expression using the `RegExp.prototype.source` of the `pattern` and adding the `'g'` flag to it. Use `String.prototype.match()` and `Array.prototype.slice()` to get the last match, if any.
+- Use `String.prototype.lastIndexOf()` to find the last occurrence of the match in the string.
+- If a match is found, use `String.prototype.slice()` and a template literal to replace the matching substring with the given `replacement`.
+- If no match is found, return the original string.
+
+```js
+const replaceLast = (str, pattern, replacement) => {
+  const match =
+    typeof pattern === 'string'
+      ? pattern
+      : (str.match(new RegExp(pattern.source, 'g')) || []).slice(-1)[0];
+  if (!match) return str;
+  const last = str.lastIndexOf(match);
+  return last !== -1
+    ? `${str.slice(0, last)}${replacement}${str.slice(last + match.length)}`
+    : str;
+};
+```
+
+```js
+replaceLast('abcabdef', 'ab', 'gg'); // 'abcggdef'
+replaceLast('abcabdef', /ab/, 'gg'); // 'abcggdef'
+replaceLast('abcabdef', 'ad', 'gg'); // 'abcabdef'
+replaceLast('abcabdef', /ad/, 'gg'); // 'abcabdef'
+```