Render _.template using object w/ numeric keys

Question

Ran into some weird behavior using underscore.js's template method:

var test = ['first', 'test'];
console.log(_.template('this is a <%= 1 %> ', test));

(Fiddle: http://jsfiddle.net/adamb/mbD6E/)

This snippets outputs: "this is a 1", while the expected result is "this is a test".

No errors are thrown. I've studied the source-code and there's no obvious explanation for this result. It's required that I use interpolation only in my template. I've tried converting the array explicitly to a collection using _.extend({}, test), but no dice.

How can I get this working?

@Jack When I explicitly convert it to an object I get the same result (as noted in the question.) Please see fiddle for that specific example. — adamb
– adamb, Commented Nov 6, 2013 at 19:51

benjaminbenben · Accepted Answer · 2013-11-06 20:05:10Z

3

You can check the compiled template code with:

_.template('this is a <%= 1 %> ').source

which gives this function:

function(obj){
var __p='';var print=function(){__p+=Array.prototype.join.call(arguments, '')};
with(obj||{}){
__p+='this is a '+
( 1 )+
' ';
}
return __p;
}

the key part is:

with(obj){
  (1)
}

because 1 isn't a valid property/variable name, it doesn't try to match the properties of the object you are templating, so just prints out '1'.

if you were to use an object like {zero: 'first', one: 'test'} and a template of 'this is a <%= one %> ', then this would look like:

with(obj){
  (one)
}

which is kind of equivelant of obj.one

edited Nov 6, 2013 at 20:05

answered Nov 6, 2013 at 19:59

benjaminbenben

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Comments

Simon Boudrias · Accepted Answer · 2013-11-06 19:53:05Z

1

A number is not a valid javascript reference.

Here you probably want to write it this way: <%= this[1] %>.

If that's not working, then pass your array to an object key:

_.template('this is a <%= list[1] %> ', { list: test })

answered Nov 6, 2013 at 19:53

Simon Boudrias

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3 Comments

Niccolò Campolungo Over a year ago

<%= this[1] %> doesn't work, while the second snippet works.

adamb Over a year ago

Although it's not a valid reference, I thought (perhaps hoped) that it would attempt to retrieve the value from the collection via bracket notation, in which case test[1] is valid.

mu is too short Over a year ago

1 is a valid expression and <%= ... %> wraps expressions.

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