Loop

A way to repeat the same code multiple times.

A control structure that repeats a block of code while a condition holds (while), a fixed number of times (for), or once per item in a collection (for-of, forEach). The condition is checked each iteration.

A backward branch in the control-flow graph. Compilers optimize loops via unrolling, hoisting loop invariants, vectorization, and strength reduction. Tail recursion is the functional equivalent and is optimized to a loop in some languages.