如何不使用 array.forEach(_ => count++) 计算 array.push？

Question

我的目标是将 actual 推undefined送到一个数组，类似于new Array(). 现在，如果你使用array.push(undefined)它并用array.forEach(element => count++)它来计数，它仍然被算作元素。function test() {  let object = [5,,,5,"hoomba"]  object.push(undefined)  let maxRetries = 0;  object.forEach(element => maxRetries++);  console.log(object);  console.log(maxRetries);}test();预期结果：console.log(object) // [5, undefined, undefined, 5, "hoomba", undefined]console.log(maxRetries) // 3实际结果：console.log(object) // [5, undefined, undefined, 5, "hoomba", undefined]console.log(maxRetries) // 4

Answer 1

undefined在计数之前添加检查（或虚假值）。

element !== undefined && maxRetries++

function test() {

  let object = [5,,,5,"hoomba"]

  object.push(undefined)

  let maxRetries = 0;

  object.forEach(element => element !== undefined && maxRetries++);

  

  // Alternatively add falsy value (null, undefined, 0, '')

  // object.forEach(element => element && maxRetries++);

  console.log(object);

  console.log(maxRetries);

}

test();

Answer 2

您可以过滤掉undefined值并计算length

function test() {

  let object = [5,,,5,"hoomba"]

  object.push(undefined)

  

  const maxRetries = object.filter(v => v !== undefined).length

  console.log('object:', object);

  console.log('maxRetries:', maxRetries);

}

test();