A JavaScript template is typically used, but not always with a MV* solution to separate parts of the view (i.e., the UI) from the logic and model (i.e., the data or JSON).
- ES6 Template Literals, the Handlebars killer? [read]
- Getting Started with nunjucks [read]
- Instant Handlebars.js [read][$]
- JavaScript Templating with Handlebars [watch][$]
- Learn Handlebars in 10 Minutes or Less [read]
- Lodash Templates [docs]
Note that JavaScript 2015 (aka ES6) has a native templating mechanism called "Templates strings". Additionally, templating as of late has been replaced by things like JSX, a template element, or HTML strings.
If I was not using React & JSX I'd first reach for JavaScript "Templates strings" and when that was lacking move to nunjucks.