JavaScript vs Python side-by-side cheat sheet

Here's a handy JavaScript vs Python side-by-side cheat sheet — perfect for quick comparisons as you switch gears.

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📝 1. Variable Declaration

Concept	JavaScript	Python
Declare a variable	let x = 5; or const x = 5;	x = 5
Dynamic typing	Yes	Yes

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🧮 2. Data Types

Type	JavaScript	Python
Number	let x = 42;	x = 42
String	"hello" or 'hello'	"hello" or 'hello'
Boolean	true, false	True, False
Null / None	null	None
Array / List	[1, 2, 3]	[1, 2, 3]
Object / Dict	{a: 1}	{"a": 1}
Undefined	undefined	No equivalent

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🔁 3. Conditionals

JavaScript	Python
if (x > 10) { ... }	if x > 10:
else if	elif
=== (strict equality)	==
!==	!=
Logical AND / OR: &&, \|\|	and, or

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🔄 4. Loops

JavaScript	Python
for (let i = 0; i < 5; i++)	for i in range(5):
for (let item of list)	for item in list:
while (x < 10)	while x < 10:
break, continue	Same

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🔧 5. Functions

JavaScript	Python
function add(a, b) { return a + b; }	def add(a, b): return a + b
Arrow function: (a, b) => a + b	Lambda: lambda a, b: a + b
function greet(name = "John")	def greet(name="John")

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🧰 6. Objects vs Dictionaries

JavaScript	Python
let person = {name: "Ana"}	person = {"name": "Ana"}
person.name or person["name"]	person["name"]

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📦 7. Arrays/Lists

JavaScript	Python
arr.length	len(arr)
arr.push(4)	arr.append(4)
arr.map(x => x * 2)	map(lambda x: x * 2, arr) or [x * 2 for x in arr]
arr.filter(x => x > 0)	filter(...) or list comprehension

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📚 8. Classes & OOP

JavaScript	Python
class Dog { constructor() {} }	class Dog:\n def __init__(self):
this.name = name	self.name = name
Method call: dog.bark()	Same: dog.bark()

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🎯 9. Common Built-ins

Task	JavaScript	Python
Print to console	console.log(x)	print(x)
Length of item	arr.length	len(arr)
Get keys of object	Object.keys(obj)	obj.keys()
Convert to string	String(5)	str(5)

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⚠️ 10. Error Handling

JavaScript	Python
try { ... } catch(e) { ... }	try:\n ...\nexcept Exception as e:

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🧠 Pythonic Tips (vs JS Thinking)

JS Habit	Pythonic Way
Use for loop with index	for i, item in enumerate(list)
Create arrays manually	Use list comprehensions
== vs === confusion	Just use == (Python handles type well)
Arrow functions everywhere	Prefer def, but use lambda for short cases
let vs const decisions	Python variables are reassigned freely