Nunjucks
A rich and powerful templating language for JavaScript
...Small 8K gzipped runtime with precompiled templates in the browser. Crazy extensible with custom filters and extensions. Everywhere available in node and all modern web browsers, with thorough precompilation options. Nunjucks allows you to port all of your existing templates from a project to something that's easier to manage. By moving your templates to the client, transfer sizes are reduced and page responsiveness increases significantly. Your API supplies data, meaning you can decouple testing the front-end from testing the back-end.