Duplicating arrays in JavaScript
Many of those who write JavaScript do not come from programming backgrounds (while I've written plenty of PHP, Python, and JavaScript, I don't have much experience with "real" programming languages*). As a result, a significant portion of JavaScript coders do not think of variables as pointers to memory addresses. This leads to confusion in cases such as this:
var fruits = ['orange', 'lime'];
var colours = fruits; // naïve attempt to duplicate array
colours.append('yellow');
One might be surprised to learn that fruits now contains not just "orange" and "lime" but also "yellow". Oops! Here's how it went wrong:
var fruits = ['orange', 'lime']; // fruits points to array containing "orange" and "lime" var colours = fruits; // colours now points to that same array!
How, then, does one create a copy of the original array? Slice!
var colours = fruits.slice();