<!DOCTYPE html><head><metacharset="utf-8"><linkrel="help"src="https://www.w3.org/TR/web-animations-1/#processing-a-keyframes-argument"><scriptsrc="/resources/testharness.js"></script><scriptsrc="/resources/testharnessreport.js"></script><scriptsrc="/web-animations/testcommon.js"></script><scriptsrc="support/testcommon.js"></script><title>Keyframes with invalid offsets</title></head><script>test(()=>{assert_throws_js(TypeError,function(){document.documentElement.animate([{offset:0.6},{offset:0.4}]);});},'Offsets must be loosely sorted');test(()=>{assert_throws_js(TypeError,function(){document.documentElement.animate([{offset:'whatever'}]);});},'Invalid offset');test(()=>{assert_throws_js(TypeError,function(){document.documentElement.animate([{offset:-1}]);});},'Offsets must be null or in the range [0,1]');</script>