数组的方法 - 删除数组中的某个元素

1. splice 方法

数组的splice方法很强大，可以进行 删除、增加、替换 操作，同时会改变原数组，返回删除/替换掉的元素组成的新数组

• 删除

  /* 删除下标为4的元素 */
  const arr = [1,2,3,4,5,6,7,8,9,10]
  const arrNew = arr.splice(4,1)
  console.log(arr, arrNew) // [1,2,3,4,6,7,8,9,10]     [5]
  
  /* 删除下标从4到6的元素 */
  const arr2 = [1,2,3,4,5,6,7,8,9,10]
  const arrNew2 = arr2.splice(4,3)
  console.log(arr2, arrNew2) // [1,2,3,4,8,9,10]     [5,6,7]
  

• 增加

  /* 下标为4处 增加一个元素 'a' */
  const arr = [1,2,3,4,5,6,7,8,9,10]
  const arrNew = arr.splice(4,0,'a')
  console.log(arr, arrNew) // [1,2,3,4,'a',5,6,7,8,9,10]    []
  
  /* 下标为4处，增加 'b','c', 'd', 'e' 这4个元素 */
  const arr2 = [1,2,3,4,5,6,7,8,9,10]
  const arrNew2 = arr2.splice(4,0,'b','c','d','e')
  const arrNew3 = arr2.splice(4,0,...['b','c','d','e'])
  console.log(arr2, arrNew2) // [1,2,3,4,'b','c','d','e',5,6,7,8,9,10]     []
  

• 替换

  /* 下标为4处元素，替换为 'a' */
  const arr = [1,2,3,4,5,6,7,8,9,10]
  const arrNew = arr.splice(4,1,'a')
  console.log(arr, arrNew) // [1,2,3,4,'a',6,7,8,9,10]    [5]
  
  /* 下标为4开始的元素，一次替换为 'b','c', 'd', 'e' 这4个元素 */
  const arr2 = [1,2,3,4,5,6,7,8,9,10]
  const arrNew2 = arr2.splice(4,4,'b','c','d','e')
  const arrNew3 = arr2.splice(4,4,...['b','c','d','e'])
  console.log(arr2, arrNew2) // [1,2,3,4,'b','c','d','e',9,10]     [5，6，7，8]
  

2. 删除下标为n的元素

const arr = [1,2,3,4,5,6,7,8,9,10]
const n = 4
const arrNew = arr.splice(4,1)
console.log(arr, arrNew)

3. 删除符合某些条件的元素

const arr = [
  { id: 1, cont: '1'},
  { id: 2, cont: '2'},
  { id: 3, cont: '3'},
  { id: 4, cont: '4'},
  { id: 5, cont: '5'}
]

删除id为3的元素

• filter
• findIdx + splice splice:会改变原数组
• reduce

const arrNew = arr.filter(item => item.id !== 3)

const idx = arr.findIndex(item => item.id === 3)
arr.splice(idx, 1)
console.log(arr)

const arrNew2 = arr.reduce((total, current) => {
  current.id !== 3 && total.push(current)
	return total
}, [])