for循环数组时使用splice时应注意的问题

const list = [

      {"className": "花花5555", "gradeName": "毕业班"},

      {"className": "中ei班", "gradeName": "毕业班"},

      {"className": "花花班5", "gradeName": "小班"},

      {"className": "花花", "gradeName": "大班"},

      {"className": "花花班", "gradeName": "中班"},

      {"className": "苹果班", "gradeName": "大班"},

      {"className": "呃呃呃", "gradeName": "中班"},

      {"className": "中二班", "gradeName": "毕业班"},

      {"className": "大一班", "gradeName": "大班"},

      {"className": "大一班1", "gradeName": "毕业班"},

      {"className": "中一班", "gradeName": "毕业班"}

    ]

for (let i = 0; i < list.length; i++) {

  if (list[i].gradeName === '毕业班') {

    list.splice(i, 1)

  }

}

console.log(JSON.stringify(list))

打印结果：[{"className":"中ei班","gradeName":"毕业班"},

{"className":"花花班5","gradeName":"小班"},

{"className":"花花","gradeName":"大班"},

{"className":"花花班","gradeName":"中班"},

{"className":"苹果班","gradeName":"大班"},

{"className":"呃呃呃","gradeName":"中班"},

{"className":"大一班","gradeName":"大班"},

{"className":"中一班","gradeName":"毕业班"}

]

发现gradeName为‘毕业班’的元素还有，这是为什么呢？

通过分析数组知道了：for循环依次进行，每次都在加1，即时数组改变，也是加1，

当i为0时，发现gradename为‘毕业班’，于是删除，数组改变了，

继续i为1时，实际上，是删除后新数组的第二个元素，也就是原数组的第三个元素，通过这可以发现，跳过了原数组的第二个元素，导致没有被循环出来，被遗忘了！

解决方案：

for (let i = 0; i < list.length; i++) {

  if (list[i].gradeName === '毕业班') {

    list.splice(i, 1)

    i = i - 1                        //满足条件时不要跳过下一个元素

  }

}

console.log(JSON.stringify(list))

打印结果：

[{"className":"花花班5","gradeName":"小班"},{"className":"花花","gradeName":"大班"},{"className":"花花班","gradeName":"中班"},{"className":"苹果班","gradeName":"大班"},{"className":"呃呃呃","gradeName":"中班"},{"className":"大一班","gradeName":"大班"}]

gradeName为‘毕业班’的都被过滤掉了！

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