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javascriptstringcoffeescriptstring-interpolation
Kaushik Shankar
Kaushik Shankar

Reputation: 5619

Why does CoffeeScript's string interpolation prefix the expression with an empty string?

In CoffeeScript, the following statement evaluates to a JavaScript statement that is prefixed by an empty string.

I feel like there is an edge case with regards to type safety, but I can't think of it off the top of my head. In what case does the prefix make a difference?

CoffeeScript:

x = "#{foo} bar"

JavaScript:

x = "" + foo + " bar";

Upvotes: 0

Views: 150

Answers (1)

Joe Lee-Moyet
Joe Lee-Moyet

Reputation: 1845

It ensures that the expression is always evaluated as a string, preventing e.g. numerical addition instead of concatenation. In the case where a string only contains a single interpolated expression, it also effectively converts that expression to a string. A couple of examples:

x = 2
y = 3

typeof "#{x}" is string   # true since this compiles to "" + x

str2 = "#{x}#{y}" # We want the string "23" here, not the number 5

Upvotes: 1

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