Add validate option (#43)

Co-authored-by: Sindre Sorhus <[email protected]>

Author: Borewit

index.d.ts

@@ -1,3 +1,14 @@
+export type Options = {
+	/**
+	Whether to validate the SVG as proper XML.
+
+	Turning this off can improve performance significantly.
+
+	@default true
+	*/
+	validate?: boolean;
+};
+
 /**
 Check if a string is [SVG](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics).
 
@@ -9,4 +20,4 @@ isSvg('<svg xmlns="http://www.w3.org/2000/svg"><path fill="#00CD9F"/></svg>');
 //=> true
 ```
 */
-export default function isSvg(string: string): boolean;
+export default function isSvg(string: string, options?: Options): boolean;

index.js

@@ -1,6 +1,6 @@
 import {XmlTextDetector} from '@file-type/xml';
 
-export default function isSvg(string) {
+export default function isSvg(string, {validate = true} = {}) {
 	if (typeof string !== 'string') {
 		throw new TypeError(`Expected a \`string\`, got \`${typeof string}\``);
 	}
@@ -11,7 +11,23 @@ export default function isSvg(string) {
 		return false;
 	}
 
-	const xmlTextDetector = new XmlTextDetector();
-	xmlTextDetector.write(string);
-	return xmlTextDetector.isValid() && xmlTextDetector.fileType?.ext === 'svg';
+	const xmlTextDetector = new XmlTextDetector({fullScan: validate});
+
+	if (validate) {
+		xmlTextDetector.write(string);
+
+		if (!xmlTextDetector.isValid()) {
+			return false;
+		}
+	} else {
+		const chunkSize = 128;
+
+		let offset = 0;
+		while (string.length > offset && !xmlTextDetector.onEnd) {
+			xmlTextDetector.write(string.slice(offset, Math.min(offset + chunkSize, string.length)));
+			offset += chunkSize;
+		}
+	}
+
+	return xmlTextDetector.fileType?.ext === 'svg';
 }

index.test-d.ts

@@ -2,3 +2,4 @@ import {expectType} from 'tsd';
 import isSvg from './index.js';
 
 expectType<boolean>(isSvg('<svg></svg>'));
+expectType<boolean>(isSvg('<svg></svg>', {validate: false}));

readme.md

@@ -16,3 +16,20 @@ import isSvg from 'is-svg';
 isSvg('<svg xmlns="http://www.w3.org/2000/svg"><path fill="#00CD9F"/></svg>');
 //=> true
 ```
+
+## API
+
+### isSvg(string, options?)
+
+#### options
+
+Type: `object`
+
+##### validate
+
+Type: `boolean`\
+Default: `true`
+
+Whether to validate the SVG as proper XML.
+
+Turning this off can improve performance significantly.