Early returns for readable functions

Originally published on php-to-js.learnio.dev — part of the PHP to JavaScript course. View this lesson on the original site.

Return as soon as you know the answer

Some PHP style guides push a single return at the bottom of a function. Early returns are equally valid in PHP and are the default habit in many JavaScript codebases — especially for parsing, validation, and lookups.

PHP habit: one exit vs early exit

<?php
function discountForRole(string $role): int {
    $percent = 0;
    if ($role === 'admin') {
        $percent = 20;
    } elseif ($role === 'member') {
        $percent = 10;
    } elseif ($role === 'guest') {
        $percent = 0;
    } else {
        return 0;
    }
    return $percent;
}

<?php
function discountForRole(string $role): int {
    if ($role === 'admin') {
        return 20;
    }
    if ($role === 'member') {
        return 10;
    }
    if ($role === 'guest') {
        return 0;
    }
    return 0;
}

Both are legal PHP. The second version maps line-for-line to JavaScript without a trailing $percent variable.

JavaScript equivalent

function discountForRole(role) {
  if (role === 'admin') return 20;
  if (role === 'member') return 10;
  if (role === 'guest') return 0;
  return 0;
}

Situation	Early return helps
Unknown role / bad input	Stop before more logic runs
Empty list	if (items.length === 0) return []
Cache hit	if (cached) return cached

Guard clauses vs early returns

Guard clauses are early returns for invalid cases. Early returns also cover happy shortcuts (found a match, nothing to do). The technique is the same: leave the function when the outcome is known.

Failure mode: returns inside loops

Returning from inside a for loop exits the whole function, not just the iteration. In PHP you might continue; in JavaScript use continue, break, or Array.prototype methods from lesson 2.11.

Try it

Use the amber Try it panel below. Click Run.

function parsePort(value) {
  if (value === '' || value == null) return { ok: false, error: 'Port required' };
  const n = Number(value);
  if (Number.isNaN(n)) return { ok: false, error: 'Port must be a number' };
  if (n < 1 || n > 65535) return { ok: false, error: 'Port out of range' };
  return { ok: true, port: n };
}

for (const v of ['', 'abc', '0', '443', '70000']) {
  console.log(v, '->', parsePort(v));
}

Each failure path returns immediately; the success path is one block at the end.

From PHP to JavaScript — Control Flow, Functions, and Scope