What is a template engine? [duplicate]

Question

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Javascript templating engines?

I keep on stumbling upon javascript templating engines and I have no idea what is their purpose. Could anyone explain me like I were five what are those? Can front-end developer make use of these?

Answer 1

JavaScript template engines are often used when writing thick JS-clients or as "normal" template engines when using server-side js like Node.js.

Instead of cluttering the code by generating HTML using string concatenating etc., you instead use a template and interpolate the variable in them.

For instance in the example bellow you pass in an array foo to the template engine which then interpolates (replaces the placeholder ${data}) with item i from the array foo:

//pseudo code <table>  <tr>    for each variable data in foo     <td>${data}</td>    end  <tr> </table> 

In frameworks like backbone.js you typically use a template to implement the view part of the MVC pattern.

There are many different types of template engines in JS. Some are direct ports of server-side frameworks like ERB, HAML etc. Others are developed specially to work with JavaScript i.e Pure

There is a debate of how much expressiveness the template engine should give you because putting logic in your templates is usually a bad thing. Because of this some template engines are specifically designed to not let you put logic in them i.e Mustache