It's a good example of how coming from different language can both help and inhibit programmer's thinking. Knowing C certainly helps to understand that repetiti

It's a good example of how coming from different language can both help and inhibit programmer's thinking. Knowing C certainly helps to understand that repetitive array size and index access is likely to be more expensive than using local variables. At the same time C programmer is more likely to adopt an imperative programming style, which is in this case more error prone, verbose and doesn't allow for code re-use. More ideomatic JavaScript would look like this: Array.prototype.foreach = function (f) { for (var i = 0, _i = this.length; i < _i; i++) f(this[i]) } /** BEGIN **/ var f = new Array(3000000); console.time(1); f.foreach( function (el) { if (el === 'foobar' || el === 'foobaz' || el === 'baz' || el === 'barfoo') // Do something }) console.timeEnd(1); /** END **/