javascript - 更简单的写法 : if (routine ! == null && routine.exercises !== undefined && routine.exercises.length > 0)

Question

有没有更简单的方法是 JavaScript:

    if (routine !== null && routine.exercises !== undefined && routine.exercises.length > 0) {
        // Do Something
    }

例如在 Dart 中我可以这样做:

    if (routine?.exercises?.length > 0 ?? 0) {
        // DO Something
    }

这意味着如果 routine 为 null 或 routine.exercises 为 null 或 routine.exercises.length 不大于 0，则只取 0 作为表达式

Answer 1

你可以做到

if (routine && routine.exercises && routine.exercises.length) ...

或更短，但可能更难阅读，使用默认值

if (((routine || {}).exercises || []).length) ...

例子:

function test(routine) {
  if (routine && routine.exercises && routine.exercises.length) {
    console.log('passed with', JSON.stringify(routine));
  }
  if (((routine || {}).exercises || []).length) {
    console.log('passed with', JSON.stringify(routine));
  }
}

test({ exercises: [1] });
test({});
test(undefined);