Use this web page to test JavaScript speechSynthesis in different browsers. JavaScript speechSynthesis is built-in to most modern browsers. But each browser is limited to different voices. Some voices do not support all of the events such as "boundary", "pause" and "resume". This web page will show you all the events that speechSynthesis dispatches with different voices that are selected. Also, try the "pause" and "resume" button with different browsers and different voices and see if the speechSynthesis.paused variable, shown on the page, changes or not.
After testing, check out CoolTTS: Combines TTS and SSML using pure JavaScript.. CoolTTS fixes many of the issues that JavaScript speechSynthesis has.