Executing javascript inside Handlebars template

Sorry to resurrect a old issue here. If you have to use handlebars or it's not feasible to change your templating library you can use Helpers from the Handlebars library.

https://handlebarsjs.com/guide/expressions.html#helpers

One of the central ideas behind handlebars and mustache is they are LOGICLESS by design and intention. They can not now, nor will they ever allow or recommend you embed raw JS in your templates. Some say this is a better design. If you want embedded javascript, almost every other traditional templating engine, such as _.template or jade or EJS is based on (or at least supports) the idea of embedded JS code snippets.