Why am I getting a Variable Not Defined Error in my Underscore Template?

Variable Not Defined Error in Underscore Template

You encountered an error when using underscore template in a Backbone.js view. The issue stems from the correct usage of template compilation in modern versions of Underscore.

In older versions of Underscore, you could use a one-step process to parse and fill in a template:

var html = _.template(template_string, data);

However, in Underscore 1.7.0 and later, the second argument to _.template is used for template options, necessitating a two-step process:

1. Compile the template:

var tmpl = _.template(template_string);

2. Execute the compiled function with data:

var html = tmpl(data);

Or, in a one-liner:

var html = _.template(template_string)(data);

In your specific case, the corrected Backbone.js view render method would be:

var V = Backbone.View.extend({
  el:'body',
  render: function () {
    var data = { lat: -27, lon: 153 };
    var tmpl = _.template('<%= lat %> <%= lon %>');
    this.$el.html(tmpl(data));
    return this;
  }
});

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