1 00:00:02,090 --> 00:00:04,370 Now that's it for functions. 2 00:00:04,370 --> 00:00:05,300 Now, I, again, 3 00:00:05,300 --> 00:00:08,290 wanna look behind the scenes of JavaScript, 4 00:00:08,290 --> 00:00:09,810 and specifically, 5 00:00:09,810 --> 00:00:14,810 I wanna explain why this kind of code worked. 6 00:00:16,329 --> 00:00:20,200 This is some code which we had in an earlier course section 7 00:00:20,200 --> 00:00:24,140 and there we have an array and we stored that array in a 8 00:00:24,140 --> 00:00:29,140 constant, and then I push a new value into that array. 9 00:00:30,730 --> 00:00:31,563 And hence, 10 00:00:31,563 --> 00:00:35,750 we clearly changed the array because we add a new value. 11 00:00:35,750 --> 00:00:38,780 Nonetheless, that code worked even though for a constant, 12 00:00:38,780 --> 00:00:41,020 you shouldn't be able to change 13 00:00:41,020 --> 00:00:43,293 the value stored in the constant. 14 00:00:44,520 --> 00:00:48,570 Now back then I explained that for arrays and also objects, 15 00:00:48,570 --> 00:00:51,830 that's kind of a special scenario and you can change 16 00:00:51,830 --> 00:00:53,690 the object and array itself. 17 00:00:53,690 --> 00:00:57,140 As long as you don't assign a new value to the constant 18 00:00:57,140 --> 00:00:59,283 itself with the equal sign. 19 00:01:00,320 --> 00:01:03,280 I now wanna explore this again and explain in greater 20 00:01:03,280 --> 00:01:06,330 detail why it works like this. 21 00:01:06,330 --> 00:01:08,480 And for this, I'll add a new file, 22 00:01:08,480 --> 00:01:09,313 which I will name 23 00:01:09,313 --> 00:01:12,143 behind-the-scenes.js, 24 00:01:13,143 --> 00:01:15,390 and in there, I'll again, 25 00:01:15,390 --> 00:01:18,900 add an array and it's an array of hobbies let's say. 26 00:01:18,900 --> 00:01:22,470 And in there I have sports and cooking. 27 00:01:22,470 --> 00:01:25,410 That's my array here. 28 00:01:25,410 --> 00:01:27,010 Now I'll do what I did before. 29 00:01:27,010 --> 00:01:31,360 And I'll push a new value into that array, for example, 30 00:01:31,360 --> 00:01:32,203 reading. 31 00:01:33,970 --> 00:01:38,860 And if we then console log, hobbies thereafter, 32 00:01:38,860 --> 00:01:43,250 you will see that if we run this behind the scenes JS file 33 00:01:43,250 --> 00:01:44,500 with node, 34 00:01:44,500 --> 00:01:48,520 we get this updated array and we don't get any error. 35 00:01:48,520 --> 00:01:50,530 Now that's what we saw before, 36 00:01:50,530 --> 00:01:53,170 but why exactly does this work? 37 00:01:53,170 --> 00:01:57,757 Why does const only care about whether we try to assign a 38 00:01:57,757 --> 00:02:00,700 new value with the equal sign, 39 00:02:00,700 --> 00:02:04,100 instead of just ensuring in general that the underlying 40 00:02:04,100 --> 00:02:05,573 value doesn't change? 41 00:02:06,810 --> 00:02:07,740 Well in the end, 42 00:02:07,740 --> 00:02:09,759 because that's how JavaScript works. 43 00:02:09,759 --> 00:02:11,560 But there also is a reason for that. 44 00:02:12,540 --> 00:02:14,770 Arrays and objects, 45 00:02:14,770 --> 00:02:16,730 and actually just like functions, 46 00:02:16,730 --> 00:02:19,350 arrays are objects under the hood, 47 00:02:19,350 --> 00:02:21,800 just special kinds of objects you could say. 48 00:02:21,800 --> 00:02:23,340 So therefore, objects, 49 00:02:23,340 --> 00:02:28,240 which include arrays are stored in a special kind of memory 50 00:02:28,240 --> 00:02:29,563 by JavaScript. 51 00:02:30,410 --> 00:02:32,740 Now we could dive super deep into that, 52 00:02:32,740 --> 00:02:34,920 but it doesn't matter too much right now. 53 00:02:34,920 --> 00:02:38,350 It's just important to keep in mind that objects 54 00:02:38,350 --> 00:02:40,640 and therefore all the arrays are stored 55 00:02:40,640 --> 00:02:42,960 in a special kind of memory. 56 00:02:42,960 --> 00:02:43,793 And for example, 57 00:02:43,793 --> 00:02:47,490 numbers or any other kind of value like strings or 58 00:02:47,490 --> 00:02:51,660 booleans are stored in a different kind of memory 59 00:02:51,660 --> 00:02:54,900 because numbers, strings and booleans, 60 00:02:54,900 --> 00:02:59,693 and a couple of other values are so-called primitive values. 61 00:03:01,250 --> 00:03:04,150 So we have our primitive values, which are numbers, 62 00:03:04,150 --> 00:03:09,150 strings and booleans and all couple of other values that 63 00:03:10,030 --> 00:03:13,770 don't matter too much right now, for example, undefined, 64 00:03:13,770 --> 00:03:17,373 which we saw before is also such a primitive value. 65 00:03:18,830 --> 00:03:22,500 And then we also have so-called the reference values, 66 00:03:22,500 --> 00:03:25,120 or reference value types, 67 00:03:25,120 --> 00:03:28,910 and that would be objects and since arrays and also 68 00:03:28,910 --> 00:03:31,110 functions are objects. 69 00:03:31,110 --> 00:03:36,110 Those values are also reference values and reference values 70 00:03:36,820 --> 00:03:40,150 are stored in a different kind of computer memory 71 00:03:40,150 --> 00:03:42,670 than primitive values are. 72 00:03:42,670 --> 00:03:44,680 The reason for that is simply that 73 00:03:44,680 --> 00:03:49,510 objects tend to be a bit more complex after all they can 74 00:03:49,510 --> 00:03:51,210 contain multiple values. 75 00:03:51,210 --> 00:03:54,973 Multiple key value pairs, maybe even some methods. 76 00:03:55,950 --> 00:03:59,140 The primitive values are really primitive. 77 00:03:59,140 --> 00:04:02,400 They are simple, it's a single number or a single string, 78 00:04:02,400 --> 00:04:06,190 even if it's a longer string, it's still pretty simple. 79 00:04:06,190 --> 00:04:09,830 And hence primitive values are stored in a more basic kind 80 00:04:09,830 --> 00:04:13,890 of computer memory. Objects are stored in a more advanced 81 00:04:13,890 --> 00:04:16,433 kind of computer memory. You could say. 82 00:04:17,790 --> 00:04:21,220 Now, because objects can and tend to be more 83 00:04:21,220 --> 00:04:22,590 complex. 84 00:04:22,590 --> 00:04:27,590 They are stored such that unnecessary copies of objects 85 00:04:28,490 --> 00:04:33,410 are avoided simply because a simple number doesn't take up a 86 00:04:33,410 --> 00:04:37,230 lot of space and memory, a complex object does. 87 00:04:37,230 --> 00:04:41,260 So we wanna avoid that we are unnecessarily copying 88 00:04:41,260 --> 00:04:42,653 objects around. 89 00:04:43,760 --> 00:04:44,593 Therefore, 90 00:04:44,593 --> 00:04:48,250 and that's now the part where this push thing combined with 91 00:04:48,250 --> 00:04:51,590 a constant will make more sense. Therefore, 92 00:04:51,590 --> 00:04:55,750 when you create an array or an object and you store it in a 93 00:04:55,750 --> 00:04:59,370 variable or a constant, what you actually stored 94 00:04:59,370 --> 00:05:04,310 there is not the value. So the object or array itself, 95 00:05:04,310 --> 00:05:09,310 but a pointer to that object or array in memory. 96 00:05:09,600 --> 00:05:14,440 So the address of that object in memory. 97 00:05:14,440 --> 00:05:16,500 You don't see that here in the code. 98 00:05:16,500 --> 00:05:19,330 It looks like the array itself is stored here, 99 00:05:19,330 --> 00:05:22,320 but that's actually not what happens. Instead. 100 00:05:22,320 --> 00:05:26,713 A pointer to the array is stored. 101 00:05:28,410 --> 00:05:31,680 If you store a number on the array or a string, 102 00:05:31,680 --> 00:05:36,680 the value itself is stored in the variable or a constant. 103 00:05:39,910 --> 00:05:41,940 Now, since that's the case, 104 00:05:41,940 --> 00:05:46,670 when you push a new value to that array, 105 00:05:46,670 --> 00:05:51,403 this value is added to the existing array in memory, 106 00:05:52,330 --> 00:05:56,610 but the pointer doesn't change, the address of that 107 00:05:56,610 --> 00:05:58,830 array in memory doesn't change. 108 00:05:58,830 --> 00:06:03,830 So the address of the array doesn't change, 109 00:06:04,770 --> 00:06:07,540 and that's why we can do that on a constant, 110 00:06:07,540 --> 00:06:09,960 because the constant stored the address, 111 00:06:09,960 --> 00:06:12,223 and the address didn't change. 112 00:06:13,290 --> 00:06:17,840 So when you call push to add a new value to an array, 113 00:06:17,840 --> 00:06:21,860 that actually tells JavaScript to look up that address, 114 00:06:21,860 --> 00:06:26,570 go to the actual array in memory and add that value there. 115 00:06:26,570 --> 00:06:30,930 The value stored in the constant did not change because that 116 00:06:30,930 --> 00:06:33,623 value is the address not the array itself. 117 00:06:34,900 --> 00:06:37,500 That's why you can do that. On the other hand, 118 00:06:37,500 --> 00:06:42,180 if you would try to set hobbies equal to a new array where 119 00:06:42,180 --> 00:06:46,180 you have coding and sleeping or something like that, 120 00:06:46,180 --> 00:06:49,200 that would not be allowed 121 00:06:49,200 --> 00:06:52,410 because here we create a new array, 122 00:06:52,410 --> 00:06:55,917 which receives its own new place in memory and which 123 00:06:55,917 --> 00:06:58,573 therefore receives and you address. 124 00:07:00,350 --> 00:07:03,360 And we would therefore try to store and you address and this 125 00:07:03,360 --> 00:07:04,193 constant, 126 00:07:04,193 --> 00:07:07,470 which is not allowed because it overrides the old value of 127 00:07:07,470 --> 00:07:10,023 the constant, which was the old address. 128 00:07:11,440 --> 00:07:15,953 So that's why we can push into an array that's stored 129 00:07:15,953 --> 00:07:18,620 in a constant because of that reference, 130 00:07:18,620 --> 00:07:21,053 whereas there's this primitive value thing. 131 00:07:22,240 --> 00:07:25,180 Now I do have a complete guide on JavaScript, 132 00:07:25,180 --> 00:07:27,680 which has 55 hours on its own, 133 00:07:27,680 --> 00:07:31,780 where I dive way deeper into JavaScript and where I also 134 00:07:31,780 --> 00:07:34,850 explain this concept in greater detail. 135 00:07:34,850 --> 00:07:37,200 We don't need all these details right now, 136 00:07:37,200 --> 00:07:40,590 but it's hopefully still clear that objects are simply 137 00:07:40,590 --> 00:07:42,860 stored differently in memories, 138 00:07:42,860 --> 00:07:45,850 than primitive values like numbers are 139 00:07:45,850 --> 00:07:47,320 and that because of that, 140 00:07:47,320 --> 00:07:50,800 and because we only store the address of the object in the 141 00:07:50,800 --> 00:07:53,410 constant, instead of the object itself, 142 00:07:53,410 --> 00:07:57,740 we can manipulate the underlying object or array without 143 00:07:57,740 --> 00:08:00,410 manipulating the constant value itself. 144 00:08:00,410 --> 00:08:04,050 Because the constant value is only that address. 145 00:08:04,050 --> 00:08:06,390 This primitive words reference value 146 00:08:06,390 --> 00:08:08,140 of thing also has a couple of important 147 00:08:08,140 --> 00:08:09,083 implications. 148 00:08:10,130 --> 00:08:14,310 Let's say we have an object now person, 149 00:08:14,310 --> 00:08:17,940 which has an age value of 32. 150 00:08:17,940 --> 00:08:20,110 Of course, that's a simple object. 151 00:08:20,110 --> 00:08:21,900 It's almost only a number, 152 00:08:21,900 --> 00:08:25,440 but still it is a object and we could have more properties 153 00:08:25,440 --> 00:08:26,590 and methods in there. 154 00:08:26,590 --> 00:08:29,203 I'm just trying to keep this simple here. 155 00:08:30,060 --> 00:08:32,679 So let's say we have this person object with potentially 156 00:08:32,679 --> 00:08:37,500 more properties, and then we have a function, not a method, 157 00:08:37,500 --> 00:08:39,409 but a standalone function here, 158 00:08:39,409 --> 00:08:42,380 which maybe gives us the number of adult years. 159 00:08:42,380 --> 00:08:46,150 This person has. So I'll name us get adult years. 160 00:08:46,150 --> 00:08:50,330 And I get a person here as a parameter, 161 00:08:50,330 --> 00:08:54,700 or let's just name it P here to avoid any confusion with the 162 00:08:54,700 --> 00:08:56,373 same name being used. 163 00:08:57,400 --> 00:09:02,400 And what I do in here is I want to get my adult years 164 00:09:04,290 --> 00:09:07,380 by setting p.age, 165 00:09:07,380 --> 00:09:09,380 because I expect P to be an object 166 00:09:09,380 --> 00:09:10,473 of that shape, 167 00:09:11,410 --> 00:09:14,983 equal to p.age minus 18. 168 00:09:16,000 --> 00:09:16,833 And hence, 169 00:09:16,833 --> 00:09:20,800 we can also use this shortcut and write it like this. 170 00:09:20,800 --> 00:09:24,690 And then I return P age, 171 00:09:24,690 --> 00:09:28,340 which is now just a number of years above 18. 172 00:09:28,340 --> 00:09:31,233 Since we deduct 18 from that age, 173 00:09:32,620 --> 00:09:37,620 if we now console log get adult years and we pass the person 174 00:09:39,110 --> 00:09:42,080 object that we created here into that, 175 00:09:42,080 --> 00:09:44,563 we should get 14 as a result. 176 00:09:46,010 --> 00:09:50,520 So if we now execute this file, indeed I do get 14 here, 177 00:09:50,520 --> 00:09:53,433 but we have a side effect here. 178 00:09:54,580 --> 00:09:59,160 Watch what happens if I also console log person after 179 00:09:59,160 --> 00:10:00,993 calling get adult years. 180 00:10:02,230 --> 00:10:05,490 If I now execute that file, we get 14 as before. 181 00:10:05,490 --> 00:10:09,160 But when I output the person here, 182 00:10:09,160 --> 00:10:14,160 I get age set equal to 14. And you might say sure, 183 00:10:14,440 --> 00:10:17,390 because that's what we did here. But on the other hand, 184 00:10:17,390 --> 00:10:21,990 we did that on the person we received as a parameter inside 185 00:10:21,990 --> 00:10:25,260 of the function, not on this person, 186 00:10:25,260 --> 00:10:29,090 this person should still have age of 32 because it's that 187 00:10:29,090 --> 00:10:31,140 person, which I'm outputting here. 188 00:10:31,140 --> 00:10:33,820 It's only the parameter value which we had inside of the 189 00:10:33,820 --> 00:10:35,650 function that changed. 190 00:10:35,650 --> 00:10:39,730 But why did this now also affect this person? 191 00:10:39,730 --> 00:10:43,393 Because objects are reference values. 192 00:10:44,240 --> 00:10:45,350 Keep in mind, 193 00:10:45,350 --> 00:10:49,410 what's stored in person in this constant here is just the 194 00:10:49,410 --> 00:10:54,020 address of that object just as we simply stored the address 195 00:10:54,020 --> 00:10:56,073 of this array and hobbies before. 196 00:10:57,230 --> 00:10:58,790 Now, since that's the case, 197 00:10:58,790 --> 00:11:02,300 what we actually pass to get adult years when we call it 198 00:11:02,300 --> 00:11:05,430 with person is the address. 199 00:11:05,430 --> 00:11:10,000 So P instead of get adult years is just the address of the 200 00:11:10,000 --> 00:11:11,570 object. 201 00:11:11,570 --> 00:11:13,760 Now, when we use the dot notation here, we can, 202 00:11:13,760 --> 00:11:14,760 of course do that. 203 00:11:14,760 --> 00:11:19,180 And JavaScript will look up the object for that address for 204 00:11:19,180 --> 00:11:22,940 us then, and give us the age property off that object. 205 00:11:22,940 --> 00:11:27,550 But when I then changed his age off this object by deducting 206 00:11:27,550 --> 00:11:29,090 18 from it, 207 00:11:29,090 --> 00:11:33,040 I do not just change the person object in this function, 208 00:11:33,040 --> 00:11:35,460 but this person object as well, 209 00:11:35,460 --> 00:11:37,500 because it's the same object. 210 00:11:37,500 --> 00:11:40,900 There is only one object because we're just working with the 211 00:11:40,900 --> 00:11:42,360 address here. 212 00:11:42,360 --> 00:11:45,460 I get the address of this person when I called get adult 213 00:11:45,460 --> 00:11:46,293 years, 214 00:11:46,293 --> 00:11:49,960 hence I'm operating on the exact person object in memory 215 00:11:49,960 --> 00:11:52,043 when I deduct 18 year. 216 00:11:53,050 --> 00:11:55,870 And that's why when I console log person there, 217 00:11:55,870 --> 00:11:59,910 after we have the updated age here in the terminal, 218 00:11:59,910 --> 00:12:02,720 because it's one and the same object, 219 00:12:02,720 --> 00:12:07,020 and that's not a bug or an unintended side effect, 220 00:12:07,020 --> 00:12:11,400 but instead that's a behavior, which we have on purpose, 221 00:12:11,400 --> 00:12:12,770 because as mentioned, 222 00:12:12,770 --> 00:12:17,160 objects can become very complex and therefore they are 223 00:12:17,160 --> 00:12:22,160 managed such that unnecessary copies are avoided. 224 00:12:22,170 --> 00:12:23,003 Hence, 225 00:12:23,003 --> 00:12:27,010 the address is pass around instead of new copies of that 226 00:12:27,010 --> 00:12:28,330 object, 227 00:12:28,330 --> 00:12:32,400 therefore operations like this can have the unintended side 228 00:12:32,400 --> 00:12:36,420 effect of changing the original object in places where we 229 00:12:36,420 --> 00:12:38,033 don't wanna do that. 230 00:12:39,310 --> 00:12:43,163 Now, how can we avoid this unintended side effect here then? 231 00:12:44,010 --> 00:12:44,843 Well, 232 00:12:44,843 --> 00:12:49,120 one work around would be that we don't update 233 00:12:49,120 --> 00:12:51,410 the person age here, but instead, 234 00:12:51,410 --> 00:12:54,430 if we just want to derive the adult years, 235 00:12:54,430 --> 00:12:56,780 instead of doing it like this, 236 00:12:56,780 --> 00:13:00,243 we can return p.age minus 18. 237 00:13:01,730 --> 00:13:06,310 It's minus 18, not minus equal. With this line of code, 238 00:13:06,310 --> 00:13:10,900 we are not setting a new value for person age. Instead, 239 00:13:10,900 --> 00:13:15,290 we are just arriving a value based on the existing age value 240 00:13:15,290 --> 00:13:16,820 minus 18, 241 00:13:16,820 --> 00:13:21,050 but that derived value does not override the age in person, 242 00:13:21,050 --> 00:13:24,900 but instead is simply returned as a value by get adult 243 00:13:24,900 --> 00:13:25,733 years. 244 00:13:27,220 --> 00:13:32,220 If we do that and we execute this file, we now have 14 here, 245 00:13:32,550 --> 00:13:36,090 but we didn't change the original object. 246 00:13:36,090 --> 00:13:38,580 That would be a better way of doing it. 247 00:13:38,580 --> 00:13:41,900 If you have a function that for some reason needs to 248 00:13:41,900 --> 00:13:44,860 manipulate the object itself, though. 249 00:13:44,860 --> 00:13:48,020 So let's say we wanna go back to that original code. 250 00:13:48,020 --> 00:13:52,460 Then you can still work around changing the original object 251 00:13:52,460 --> 00:13:57,433 by passing in a copy of person into get adult years. 252 00:13:58,420 --> 00:13:59,253 And to do that. 253 00:13:59,253 --> 00:14:02,260 You just need to create a new object by again, 254 00:14:02,260 --> 00:14:04,610 using the curly braces here, 255 00:14:04,610 --> 00:14:09,260 where you either add all the properties manually. 256 00:14:09,260 --> 00:14:11,980 So where you add an age property and set this equal to 257 00:14:11,980 --> 00:14:14,830 person dot age with that, 258 00:14:14,830 --> 00:14:17,600 we are creating a brand new object, 259 00:14:17,600 --> 00:14:21,180 a brand new place in memory with a brand new separate 260 00:14:21,180 --> 00:14:22,250 address. 261 00:14:22,250 --> 00:14:26,270 And we just populate age based on the values stored in 262 00:14:26,270 --> 00:14:30,140 persons age. But that is then a number which we use here. 263 00:14:30,140 --> 00:14:30,973 So with that, 264 00:14:30,973 --> 00:14:33,190 we're not pointing at the old person object 265 00:14:33,190 --> 00:14:35,820 as a whole in this place. 266 00:14:35,820 --> 00:14:40,600 And therefore, if we now would save that and run this code, 267 00:14:40,600 --> 00:14:42,260 it would work without issues. 268 00:14:42,260 --> 00:14:44,903 And the original object wasn't changed, 269 00:14:46,640 --> 00:14:49,070 but creating objects like this, 270 00:14:49,070 --> 00:14:52,080 and manually adding all the properties 271 00:14:52,080 --> 00:14:56,240 which the original object has into this new object can be 272 00:14:56,240 --> 00:14:57,433 very cumbersome. 273 00:14:58,540 --> 00:15:01,730 That's why we can use another operator here, 274 00:15:01,730 --> 00:15:06,730 which we already saw before. Between those curly braces, 275 00:15:07,020 --> 00:15:11,820 we can use the free dot operator, the spread operator, 276 00:15:11,820 --> 00:15:15,903 and spread our person object into this new object. 277 00:15:17,210 --> 00:15:18,043 Now, 278 00:15:18,043 --> 00:15:22,020 we haven't seen this usage of the spread operator before, 279 00:15:22,020 --> 00:15:26,060 but the spread operator can indeed be used on arrays 280 00:15:26,060 --> 00:15:29,660 or on objects and on arrays. 281 00:15:29,660 --> 00:15:34,660 As you saw before. It pulls out all the individual values to 282 00:15:35,260 --> 00:15:37,223 create a list of values. 283 00:15:38,080 --> 00:15:39,830 When used on objects, 284 00:15:39,830 --> 00:15:44,730 it pulls out all the key value pairs off the object and 285 00:15:44,730 --> 00:15:47,950 gives you a list of those key value pairs. 286 00:15:47,950 --> 00:15:50,550 And if you do that between curly braces, 287 00:15:50,550 --> 00:15:52,670 you create a new object, 288 00:15:52,670 --> 00:15:56,870 which gets a list of all the key value pairs of another 289 00:15:56,870 --> 00:15:57,820 object. 290 00:15:57,820 --> 00:16:01,850 And hence you get a new object in memory with a new address 291 00:16:01,850 --> 00:16:05,733 with all the old key value pairs of another object. 292 00:16:06,630 --> 00:16:11,280 That's a way of copying an object, of creating a brand new 293 00:16:11,280 --> 00:16:12,830 object of the same shape 294 00:16:12,830 --> 00:16:15,460 in a new place in memory and therefore that's 295 00:16:15,460 --> 00:16:20,260 another way of working around that issue in quotes, 296 00:16:20,260 --> 00:16:22,180 because it's not really an issue. 297 00:16:22,180 --> 00:16:24,540 It's an intended feature 298 00:16:24,540 --> 00:16:28,670 of having reference values for objects. 299 00:16:28,670 --> 00:16:31,860 If we now execute this file here again, 300 00:16:31,860 --> 00:16:35,960 we have the unchanged original object whilst also getting 301 00:16:35,960 --> 00:16:37,623 the correct adult years. 302 00:16:38,480 --> 00:16:42,250 With that code that changes the object. 303 00:16:42,250 --> 00:16:45,930 It does not change the original object anymore because we 304 00:16:45,930 --> 00:16:50,930 create a brand new object based on the original object here 305 00:16:51,000 --> 00:16:52,913 in this line, 21 now. 306 00:16:53,910 --> 00:16:54,743 And again, 307 00:16:54,743 --> 00:16:58,860 that is certainly a bit more advanced and can be challenging 308 00:16:58,860 --> 00:17:02,340 to grasp or to see why that's helpful. 309 00:17:02,340 --> 00:17:05,960 But we are going to write more and more advanced code over 310 00:17:05,960 --> 00:17:09,619 the next sections. And as a web developer in general, 311 00:17:09,619 --> 00:17:13,000 you will be confronted with more advanced code like this, 312 00:17:13,000 --> 00:17:16,390 and therefore you should be aware of this primitive versus 313 00:17:16,390 --> 00:17:18,260 reference value thing. 314 00:17:18,260 --> 00:17:22,380 And you also should know how you can create copies and work 315 00:17:22,380 --> 00:17:25,790 around that reference value limitation, 316 00:17:25,790 --> 00:17:28,130 which is sometimes face to avoid 317 00:17:28,130 --> 00:17:31,450 unintended side effects as we had them at the 318 00:17:31,450 --> 00:17:35,440 beginning, when we changed the original object, 319 00:17:35,440 --> 00:17:36,760 because you very often 320 00:17:36,760 --> 00:17:39,013 wanna avoid doing something like that.