Use var, it reduces the scope of the variable otherwise the variable looks up to the nearest closure searching for a var statement. If it cannot find a var then it is global (if you are in a strict mode, using strict, global variables throw an error). This can lead to problems like the following. … Read more
Don’t use for..in for Array iteration. It’s important to understand that Javascript Array’s square bracket syntax ([]) for accessing indicies is actually inherited from the Object… obj.prop === obj[‘prop’] // true The for..in structure does not work like a more traditional for..each/in that would be found in other languages (php, python, etc…). Javascript’s for..in is … Read more
The current answers are good, but do not talk about how they are just syntactic sugar to some pattern that we are so used to. Let’s start with an example, say we have 10 numbers, and we want a subset of those that are greater than, say, 5. >>> numbers = [12, 34, 1, 4, … Read more