Category Archives: Underscore

ERB Delimiters in Template Underscore

Now that we know how to create a generic template let’s look at some ERB delimiters.

The _.template function has 3 arguments:

  1. String text : the template string
  2. Object data : the evaluation data
  3. Object settings : local settings, the _.templateSettings is the global settings object

If no data (or null) given, than a render function will be returned. It has 1 argument:

  1. Object data : same as the data above

There are 3 regex patterns and 1 static parameter in the settings:

  1. RegExp evaluate : “<%code%>” in template string
  2. RegExp interpolate : “<%=code%>” in template string
  3. RegExp escape : “<%-code%>”
  4. String variable : optional, the name of the data parameter in the template string

The code in an evaluate section will be simply evaluated. You can add string from this section with the__p+=”mystring” command to the evaluated template, but this is not recommended (not part of the templating interface), use the interpolate section instead of that. This type of section is for adding blocks like if or for to the template.

The result of the code in the interpolate section will added to the evaluated template. If null given back, then empty string will added.

The escape section escapes html with _.escape on the return value of the given code. So its similar than an _.escape(code) in an interpolate section, but it escapes with \ the whitespace characters like\n before it passes the code to the _.escape. I don’t know why is that important, it’s in the code, but it works well with the interpolate and _.escape – which doesn’t escape the white-space characters – too.

By default the data parameter is passed by a with(data){…} statement, but this kind of evaluating is much slower than the evaluating with named variable. So naming the data with the variable parameter is something good…

For example:

var html = _.template(
    "<pre>The \"<% __p+=_.escape(o.text) %>\" is the same<br />" +
        "as the  \"<%= _.escape(o.text) %>\" and the same<br />" +
        "as the \"<%- o.text %>\"</pre>",
        text: "<b>some text</b> and \n it's a line break"
        variable: "o"



The "<b>some text</b> and 
 it's a line break" is the same
as the "<b>some text</b> and 
 it's a line break" and the same
as the "<b>some text</b> and 
 it's a line break"

You can find here more examples how to use the template and override the default settings:

By template loading you have many options, but at the end you always have to convert the template into string. You can give it as normal string like the example above, or you can load it from a script tag, and use the .html() function of jquery, or you can load it from a separate file with the tpl plugin of require.js.

Another option to build the dom tree with laconic instead of templating.

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Posted by on August 22, 2014 in Javascript, Underscore