Performance overhead can absolutely be ignored... if you don't care about the majority of your users. Usage is moving more and more to mobile devices, which are less powerful than desktops and laptops. They are also battery powered, and the more work the mobile browsers are being asked to do, the more it eats into that battery life.
Is readability of the code (and map is really no more readable than a foreach) really more important than the user base of the final product?
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Performance overhead can absolutely be ignored... if you don't care about the majority of your users. Usage is moving more and more to mobile devices, which are less powerful than desktops and laptops. They are also battery powered, and the more work the mobile browsers are being asked to do, the more it eats into that battery life.
Is readability of the code (and map is really no more readable than a foreach) really more important than the user base of the final product?