index parameter of CSSStyleSheet.insertRule is now optional

Author: DiogoDoreto

.changeset/tricky-buttons-clap.md

@@ -0,0 +1,5 @@
+---
+"rrweb-cssom": patch
+---
+
+`index` parameter of `CSSStyleSheet.insertRule` is now optional

lib/CSSStyleSheet.js

@@ -37,6 +37,9 @@ CSSOM.CSSStyleSheet.prototype.constructor = CSSOM.CSSStyleSheet;
  * @return {number} The index within the style sheet's rule collection of the newly inserted rule.
  */
 CSSOM.CSSStyleSheet.prototype.insertRule = function(rule, index) {
+	if (index === void 0) {
+		index = 0;
+	}
 	if (index < 0 || index > this.cssRules.length) {
 		throw new RangeError("INDEX_SIZE_ERR");
 	}

spec/CSSStyleSheet.spec.js

@@ -24,6 +24,15 @@ describe('CSSStyleSheet', function() {
 			s.insertRule("a {color: blue}", 0);
 			expect(s.cssRules[0].parentStyleSheet).toBe(s);
 		});
+
+		it('should insert in index 0 by default', function () {
+			var s = new CSSOM.CSSStyleSheet;
+			s.insertRule("a {color: blue}", 0);
+
+			var insertedIndex = s.insertRule("b {color: black;}");
+			expect(insertedIndex).toEqual(0);
+			expect(s.cssRules[0].cssText).toEqual("b {color: black;}");
+		})
 	});
 });
 });