sprint 2 solutions

Author: Yama948

Sprint-2/1-key-exercises/1-count.js

@@ -3,4 +3,12 @@ let count = 0;
 count = count + 1;
 
 // Line 1 is a variable declaration, creating the count variable with an initial value of 0
-// Describe what line 3 is doing, in particular focus on what = is doing
+// Describe what line 3 is doing, in particular focus on what = means
+// 
+= means "put this value in the box."
+
+Line 3 is saying: take whatever's currently in the `count` box (that's `0`), add 1 to it, and shove the answer back in the same box.
+
+So it goes: `0 + 1 = 1`, and now `count` holds `1` instead of `0`.
+
+That's really it — `=` in code just means "store this," not "these are the same thing."

Sprint-2/1-key-exercises/2-initials.js

@@ -7,4 +7,12 @@ const lastName = "Johnson";
 
 const initials = ``;
 
-// https://www.google.com/search?q=get+first+character+of+string+mdn
+// https://www.google.com/search?q=get+first+character+of+string
+// 
+ grab the first letter of each string using `[0]`, and glue them together:
+
+```javascript
+const initials = firstName[0] + middleName[0] + lastName[0];
+```
+
+`firstName[0]` grabs whatever's sitting at position 0 in the string — the first letter — so that's `"C"`. Same deal for the other two, giving you `"K"` and `"J"`. The `+` just sticks the three letters together into one string, so you end up with `"CKJ"` 

Sprint-2/1-key-exercises/3-paths.js

@@ -20,4 +20,7 @@ console.log(`The base part of ${filePath} is ${base}`);
 const dir = ;
 const ext = ;
 
-// https://www.google.com/search?q=slice+mdn
+// https://www.google.com/search?q=slice+mdn
+
+const dir = filePath.slice(0, lastSlashIndex);
+const ext = base.slice(base.lastIndexOf("."));

Sprint-2/1-key-exercises/4-random.js

@@ -7,3 +7,8 @@ const num = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
 // Try breaking down the expression and using documentation to explain what it means
 // It will help to think about the order in which expressions are evaluated
 // Try logging the value of num and running the program several times to build an idea of what the program is doing
+
+Math.random() gives you a random decimal between 0 and just-under-1 — like 0.628.... 
+Then you multiply that by 100 (which is maximum - minimum + 1), stretching it out into a decimal between 0 and just-under-100. 
+Math.floor() chops off everything after the decimal point, rounding down, you've got a whole number from 0 to 99.
+ + minimum (which is +1) shifts the whole thing up by one, so instead of 0–99 you get 1–100.

Sprint-2/2-mandatory-errors/0.js

@@ -1,2 +1,4 @@
 This is just an instruction for the first activity - but it is just for human consumption
-We don't want the computer to run these 2 lines - how can we solve this problem?
+We don't want the computer to run these 2 lines - how can we solve this problem?
+
+by adding // infront of each line before writing a text/code

Sprint-2/2-mandatory-errors/1.js

@@ -2,3 +2,12 @@
 
 const age = 33;
 age = age + 1;
+
+const means "this value is locked in, you can't change it later." So when line 2 tries to reassign age, JavaScript throws:
+
+TypeError: Assignment to constant variable.
+//instead use 'let' i.e let age = 33;
+age = age + 1;
+
+console.log(age); // 34
+const for stuff that stays the same, let for stuff that's meant to change such as age.

Sprint-2/2-mandatory-errors/2.js

@@ -3,3 +3,6 @@
 
 console.log(`I was born in ${cityOfBirth}`);
 const cityOfBirth = "Bolton";
+
+ReferenceError: Cannot access 'cityOfBirth' before initialization
+JavaScript reads top to bottom, so at the point it hits that console.log, cityOfBirth doesn't exist yet.

Sprint-2/2-mandatory-errors/3.js

@@ -7,3 +7,12 @@ const last4Digits = cardNumber.slice(-4);
 // Then run the code and see what error it gives.
 // Consider: Why does it give this error? Is this what I predicted? If not, what's different?
 // Then try updating the expression last4Digits is assigned to, in order to get the correct value
+
+cardNumber is just a plain number, and .slice() only exists on strings and arrays, not numbers
+'TypeError: cardNumber.slice is not a function'
+numbers just don't have a .slice() method built in.
+
+const cardNumber = 4533787178994213;
+const last4Digits = cardNumber.toString().slice(-4);
+
+console.log(last4Digits); // "4213"

Sprint-2/2-mandatory-errors/4.js

@@ -1,2 +1,4 @@
 const 12HourClockTime = "8:53pm";
 const 24hourClockTime = "20:53";
+
+it'll throw a SyntaxError before anything executes, because both variable names start with a number.

Sprint-2/3-mandatory-interpret/1-percentage-change.js

@@ -20,3 +20,9 @@ console.log(`The percentage change is ${percentageChange}`);
 // d) Identify all the lines that are variable declarations
 
 // e) Describe what the expression Number(carPrice.replaceAll(",","")) is doing - what is the purpose of this expression?
+
+a) 5 calls across 3 lines
+b) error is on line 5, there's a missing comma between ',' and ""
+c)reassignments on line 4 and 5
+d) declarations on lines 1,2,7,8
+e) carPrice starts as the string "10,000" — you can't do maths on that as-is, the comma would mess things up. So first, .replaceAll(",", "") strips out the comma, leaving "10000". Then Number(...) converts that string into an actual number, 10000, that you can subtract and divide like normal.