Loop with index

2 snippets across 2 stacks — JavaScript, Python

JSJavaScript

for Loop

syntax

for (init; condition; update) { ... }

example

const items = ["apple", "banana", "cherry"];
for (let i = 0; i < items.length; i++) {
  console.log(`${i + 1}. ${items[i]}`);
}

output

"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.

PYPython

Useful List Operations

PY · Lists

syntax

len() / in / enumerate() / zip()

example

items = ["pen", "notebook", "eraser"]
print(len(items))
print("pen" in items)

for idx, item in enumerate(items, start=1):
    print(f"{idx}. {item}")

output

3
True
1. pen
2. notebook
3. eraser

Note enumerate() gives (index, value) pairs. Pass start= to begin counting from a number other than 0.