feat: support replace method (#203)

README.md

@@ -161,6 +161,24 @@ Same as `s.appendLeft(...)`, except that the inserted content will go *before* a
 
 Same as `s.appendRight(...)`, except that the inserted content will go *before* any previous appends or prepends at `index`
 
+### s.replace( regexp, substitution )
+
+String replacement with RegExp or string, a replacer function is also supported. Returns `this`.
+
+```ts
+import MagicString from 'magic-string'
+
+const s = new MagicString(source)
+
+s.replace(foo, 'bar')
+s.replace(/foo/g, 'bar')
+s.replace(/(\w)(\d+)/g, (_, $1, $2) => $1.toUpperCase() + $2)
+```
+
+The differences from [`String.replace`]((https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace)):
+- It will always match against the **original string**
+- It mutates the magic string state (use `.clone()` to be immutable)
+
 ### s.remove( start, end )
 
 Removes the characters from `start` to `end` (of the original string, **not** the generated string). Removing the same content twice, or making removals that partially overlap, will cause an error. Returns `this`.

index.d.ts

@@ -204,6 +204,10 @@ export default class MagicString {
    * Removes empty lines from the start and end.
    */
   trimLines(): MagicString;
+  /**
+   * String replacement with RegExp or string.
+   */
+  replace(regex: RegExp | string, replacement: string | ((substring: string, ...args: any[]) => string)): MagicString;
 
   lastChar(): string;
   lastLine(): string;

src/MagicString.js

@@ -712,4 +712,46 @@ export default class MagicString {
 		this.trimStartAborted(charType);
 		return this;
 	}
+
+	replace(searchValue, replacement) {
+		function getReplacement(match) {
+			if (typeof replacement === 'string') {
+				return replacement.replace(/\$(\$|&|\d+)/g, (_, i) => {
+					// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#specifying_a_string_as_a_parameter
+					if (i === '$')
+						return '$';
+					if (i === '&')
+						return match[0];
+					const num = +i;
+					if (num < match.length)
+						return match[+i];
+					return `$${i}`;
+				});
+			}
+			else {
+				return replacement(...match);
+			}
+		}
+		function matchAll(re, str) {
+			let match;
+			const matches = [];
+			while (match = re.exec(str)) {
+				matches.push(match);
+			}
+			return matches;
+		}
+		if (typeof searchValue !== 'string' && searchValue.global) {
+			const matches = matchAll(searchValue, this.original);
+			matches.forEach((match) => {
+				if (match.index != null)
+					this.overwrite(match.index, match.index + match[0].length, getReplacement(match));
+			});
+		}
+		else {
+			const match = this.original.match(searchValue);
+			if (match && match.index != null)
+				this.overwrite(match.index, match.index + match[0].length, getReplacement(match));
+		}
+		return this;
+	}
 }

test/MagicString.js

@@ -1277,4 +1277,40 @@ describe('MagicString', () => {
 			assert.equal(s.lastLine(), '//lastline');
 		});
 	});
+
+	describe('replace', () => {
+		it('works with string replace', () => {
+			const code = '1 2 1 2';
+			const s = new MagicString(code);
+
+			s.replace('2', '3');
+
+			assert.strictEqual(s.toString(), '1 3 1 2');
+		});
+
+		it('works with global regex replace', () => {
+			const s = new MagicString('1 2 3 4 a b c');
+
+			s.replace(/(\d)/g, 'xx$1$10');
+
+			assert.strictEqual(s.toString(), 'xx1$10 xx2$10 xx3$10 xx4$10 a b c');
+		});
+
+		it('works with global regex replace $$', () => {
+			const s = new MagicString('1 2 3 4 a b c');
+
+			s.replace(/(\d)/g, '$$');
+
+			assert.strictEqual(s.toString(),'$ $ $ $ a b c');
+		});
+
+		it('works with global regex replace function', () => {
+			const code = 'hey this is magic';
+			const s = new MagicString(code);
+
+			s.replace(/(\w)(\w+)/g, (_, $1, $2) => `${$1.toUpperCase()}${$2}`);
+
+			assert.strictEqual(s.toString(),'Hey This Is Magic');
+		});
+	});
 });