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Editorial Team
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Asked: 2026-06-12T02:50:54+00:00

This coffeescript: if typeof(groups) is undefined or groups.length == 0 gets compiled into the

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This coffeescript:

if  typeof(groups) is undefined or groups.length == 0

gets compiled into the following javascript:

if (typeof groups === void 0 || groups.length === 0)

Basically i want to check if the groups array is null or empty and hoping that if the first condition is true, the second condition will not be checked (short-circuiting). However Chrome throws the following error:

Uncaught type error: Cannot read property length of undefined

Any insights on why it wouldnt short-circuit?

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1 Answer

  1. Editorial Team

    CoffeeScript has an operator that takes care of this case for you. If you use:

    unless groups?.length > 0

    it will form what you’re looking for, taking care of the undefined/null cases and only trying groups.length if groups is defined. This has the advantage of being easily chained:

    if foo?.bar?.length > 0
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