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🟨 JavaScript - Code Walkthrough

50 code tracing challenges — guess the output!

TitleAction
1
String Building in a Loop
easy○ Not StartedLoopsPractice
2
Array push and length
easy○ Not StartedArraysPractice
3
typeof a String
easy○ Not StartedVariablesPractice
4
Template Literal Output
easy○ Not StartedPrintingPractice
11
Integer Division with Math.floor
easy○ Not StartedOperatorsPractice
12
Summing with a For Loop
easy○ Not StartedLoopsPractice
13
Plus Means Add or Concatenate
easy○ Not StartedOperatorsPractice
14
Writing to an Array Slot
easy○ Not StartedArraysPractice
15
Two Ternary Expressions
easy○ Not StartedOperatorsPractice
16
typeof on Different Values
easy○ Not StartedOperatorsPractice
17
Truthy and Falsy in if
easy○ Not StartedIf StatementsPractice
18
Divisible by Three in a Loop
easy○ Not StartedLoopsPractice
19
String Length and Indexing
easy○ Not StartedStringsPractice
20
Breaking Out of a Loop
easy○ Not StartedLoopsPractice
36
Division Always Gives a Float
easy○ Not StartedOperatorsPractice
37
Plus Sign: Add or Concatenate
easy○ Not StartedOperatorsPractice
38
Counting Down in a Loop
easy○ Not StartedLoopsPractice
39
Remainders with Modulo
easy○ Not StartedOperatorsPractice
40
Comparisons Return Booleans
easy○ Not StartedOperatorsPractice
41
Reading Past the End of an Array
easy○ Not StartedArraysPractice
5
map then join
medium○ Not StartedArraysPractice
6
reduce to a Sum
medium○ Not StartedArraysPractice
7
Short-Circuit with OR
medium○ Not StartedOperatorsPractice
8
Objects Are References
medium○ Not StartedVariablesPractice
21
Switch Statement Fall-Through
medium○ Not StartedSwitchPractice
22
Factorial by Recursion
medium○ Not StartedRecursionPractice
23
Two Names for One Array
medium○ Not StartedArraysPractice
24
var Hoisting Inside a Function
medium○ Not StartedScopePractice
25
Post-Increment as an Array Index
medium○ Not StartedOperatorsPractice
26
NaN Is Never Equal
medium○ Not StartedOperatorsPractice
27
parseInt Versus Number
medium○ Not StartedCastingPractice
29
Counting Ordered Pairs
medium○ Not StartedLoopsPractice
30
Method Mutating this
medium○ Not StartedObjectsPractice
31
slice Copies, splice Cuts
medium○ Not StartedArraysPractice
42
Chained Ternary Operators
medium○ Not StartedIf StatementsPractice
43
Switch Without a Break
medium○ Not StartedIf StatementsPractice
44
var Hoisting Inside a Function
medium○ Not StartedFunctionsPractice
45
Array Aliasing vs a Copy
medium○ Not StartedArraysPractice
46
Loose Equality Coercions
medium○ Not StartedOperatorsPractice
47
Post- and Pre-Increment Together
medium○ Not StartedOperatorsPractice
50
Shrinking an Array with length
medium○ Not StartedArraysPractice
9
Closures Capturing let
hard○ Not StartedFunctionsPractice
10
Default Sort Is Lexicographic
hard○ Not StartedArraysPractice
28
Loose Equality Coercion
hard○ Not StartedOperatorsPractice
32
Floating-Point Addition
hard○ Not StartedOperatorsPractice
33
Building a Fibonacci Sequence
hard○ Not StartedRecursionPractice
34
Destructuring with Rest
hard○ Not StartedArraysPractice
35
Logical Operators Return Values
hard○ Not StartedOperatorsPractice
48
A Closure Keeps Private State
hard○ Not StartedFunctionsPractice
49
Coercion in Mixed Expressions
hard○ Not StartedCastingPractice