We've seen that you cannot reassign a constant variable in the case of a number 0:00 or a string. 0:05 The same goes for any value of a constant variable. 0:05 You cannot reassign strings, numbers, booleans, objects, and arrays. 0:09 Unlike strings, numbers, and booleans, objects in arrays have methods and 0:14 properties that modify the objects or array. 0:18 Do they still work with const? 0:22 First we'll declare a variable, which is a constant called days. 0:24 This will contain an array with a single string "Monday". 0:33 Second we'll declare another constant variable 0:39 person that contains an object literal with a {first_name}. 0:44 Key, with the string "Imogen". 0:52 Let's attempt to modify these in the console here, first days. 0:59 Let's use the push method to add another day to the array. 1:06 It didn't error, it returned the number 2, meaning the new array length. 1:14 If we type days, and hit Enter, we get Monday and Tuesday returned. 1:21 Let's try and add a last_name property to the person object. 1:28 Again no error. 1:36 When we type person and hit Enter we get an object 1:38 literal back with the first_name and last_name properties. 1:42 So what's happening here? 1:47 Const doesn't prevent complex objects like arrays and objects from being modified. 1:49 It just prevents them from being reassigned or over written completely. 1:55 For example, when I attempt to override 2:00 person with another object literal. 2:06 It shows an error, because I'm attempting to re-assign person with a new object. 2:16 However, if I modified the first name. 2:25 To equal another value, Andrew, I don't get any errors. 2:32