support getting magic string length

index.d.ts

@@ -49,6 +49,7 @@ export class Bundle {
   trimStart(charType?: string): Bundle;
   trimEnd(charType?: string): Bundle;
   isEmpty(): boolean;
+  length(): number;
 }
 
 export type ExclusionRange = [ number, number ];
@@ -96,6 +97,7 @@ export default class MagicString {
   lastChar(): string;
   lastLine(): string;
   isEmpty(): boolean;
+  length(): number;
 
   original: string;
 }

src/Bundle.js

@@ -235,6 +235,10 @@ export default class Bundle {
 		return true;
 	}
 
+	length() {
+		return this.sources.reduce((length, source) => length + source.content.length(), this.intro.length);
+	}
+
 	trimLines() {
 		return this.trim('[\\r\\n]');
 	}

src/MagicString.js

@@ -632,6 +632,15 @@ export default class MagicString {
 		return true;
 	}
 
+	length() {
+		let chunk = this.firstChunk;
+		let length = 0;
+		do {
+			length += chunk.intro.length + chunk.content.length + chunk.outro.length;
+		} while (chunk = chunk.next);
+		return length;
+	}
+
 	trimLines() {
 		return this.trim('[\\r\\n]');
 	}

test/MagicString.js

@@ -1192,6 +1192,25 @@ describe( 'MagicString', () => {
 		});
 	});
 
+	describe( 'length', () => {
+		it( 'should support length', () => {
+			const s = new MagicString( ' abcde   fghijkl ' );
+
+			assert.equal( s.length(), 17 );
+
+			s.prepend( '  ' );
+			s.append( '  ' );
+			s.remove( 1, 6 );
+			s.remove( 9, 15 );
+
+			assert.equal( s.length(), 6 );
+
+			s.remove( 15, 16 );
+
+			assert.equal( s.length(), 5 );
+		});
+	});
+
 	describe( 'lastLine', () => {
 		it( 'should support lastLine', () => {
 			const s = new MagicString( ' abcde\nfghijkl ' );