4 snippets across 2 stacks - JavaScript, Python
Also written as for in loop · for of loop
for (init; condition; update) { ... }const items = ["apple", "banana", "cherry"];
for (let i = 0; i < items.length; i++) {
console.log(`${i + 1}. ${items[i]}`);
}"1. apple"
"2. banana"
"3. cherry"Note Classic loop when you need the index. For simple iteration, prefer for...of. Cache .length in the initializer if the array is very large and not changing.
for (const element of iterable) { ... }const scores = [88, 92, 75, 100];
let sum = 0;
for (const score of scores) {
sum += score;
}
console.log(`Average: ${sum / scores.length}`);
// Works with strings too
for (const char of "hello") {
process(char);
}"Average: 88.75"Note Works on any iterable: arrays, strings, Maps, Sets, generators. Does NOT work on plain objects -- use Object.entries() or for...in for those.
for (const key in object) { ... }const theme = { primary: "#3498db", secondary: "#2ecc71", accent: "#e74c3c" };
for (const colorName in theme) {
console.log(`${colorName}: ${theme[colorName]}`);
}"primary: #3498db"
"secondary: #2ecc71"
"accent: #e74c3c"Note Iterates over enumerable string properties, including inherited ones. Avoid for arrays (use for...of). Use Object.hasOwn() to filter inherited keys.
for item in iterable:
...total = 0
prices = [12.50, 8.99, 24.00]
for price in prices:
total += price
print(f"Total: ${total:.2f}")
for i in range(3):
print(f"Attempt {i + 1}")Total: $45.49
Attempt 1
Attempt 2
Attempt 3Note range(n) produces 0 through n-1. Use range(start, stop, step) for more control. Python for loops iterate over any iterable, not just numeric ranges.