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..and why shouldn't: if (someStr.indexOf("John") !== -1) { ... } vs if (someStr.indexOf("John")) { ... } Or when _teaching_ it's kind of funny saying "So, w

• icebraining 11y ago
  Your example should really be (using a polyfill if necessary) if(someStr.includes('John')) {...} While I don't mind it for containers, I've never liked using Boolean coercion for numbers. Zero is obviously a special case, but I don't think it maps well with the True/False dichotomy.
  • jewel 11y ago
    Zero doesn't have to be a special case. In ruby 0 is a truthy value, as well as the empty string. The only things that are falsey are false and nil. Truthy/falsey means when used in a conditional or after a unary !. So you still get strong typing, e.g. false == nil is not a true statement.
• ufo 11y ago
  Option #2 assumes that 0 is falsy. Its an OK assumption for a language like C but for languages that let lots of different things go into an if condition I prefer for zero to be truthy and just false / null / etc to be falsy.
  • JoshTriplett 11y ago
    Banning implicit integer conversions, such that neither 0 nor 1 can be used in a conditional, isn't unreasonable; then you have to write a boolean operator or conversion explicitly. However, if you allow integers in conditionals, yet have 0 mean true, you will break the default expectations of far too many programmers.
    • jfarmer 11y ago
      The first several languages I learned treated 0 as falsey and I can't really recall it tripping me up when I learned a language (Ruby) where that's not the case. I suppose always thought of 0-as-false as an unfortunate consequence of C not having a native boolean type, anyhow.
    • ufo 11y ago
      In a statically typed language, restricting if conditionals to just booleans is the approach I like the most: simple and safe. On the other hand, in dynamic languages, where you can pass anything to conditional I think that treating 0 as falsy is very error prone. For example, its very common to use conditionals to implement default values: function foo(name){ name = name || "default name"; } In this setting, having 0 and "" act as falsy is a bug waiting to happen. On the other hand, having 0 act as truthy might confuse you a bit the first time you come across it but its an easy fix (just write x != 0 instead) and its not very likely to hit you when you don't expect it.
      • JoshTriplett 11y ago
        If your language has something like "None" or "null", then you should be checking against that to implement a default, rather than checking a truth value. After all, what if you wanted to implement a boolean parameter with a default value? Personally, I'm a big fan of languages with a "Maybe" type for this kind of thing.
        • deleted 11y ago
          [deleted]
        • ufo 11y ago
          The `||` pattern is super common in a bunch of languages though and to code it with a `== null` test you would need to expand it to a full blown ternary operator name != null ? name : "default name" Some languages have a "null-coalescing" operator you can use in these cases but its a niche thing. (And I agree with you on the Maybe thing but, as I said previously, 0 in conditionals is not a problem when conditionals have to be boolean)