Question

我有这个数组：

let items = ["apple", "orange", "watermelon", "blueberry", "lemon", "guava"];

，我想从第一个索引中顺序删除数组值。它将产生：

[ "apple", "orange", "watermelon", "blueberry", "lemon", "guava" ]
[ "orange", "watermelon", "blueberry", "lemon", "guava" ]
[ "watermelon", "blueberry", "lemon", "guava" ]
[ "blueberry", "lemon", "guava" ]
[ "lemon", "guava" ]
[ "guava" ]

我已经尝试过此代码：

let items = ["apple", "orange", "watermelon", "blueberry", "lemon",   "guava"];

runLoop = async () => {
for(const item of items){
        await new Promise( resolve => setTimeout( resolve, 1000 ));
        console.log(items);
        remove(items, item);
        console.log('------------');
    }
 }

 function remove(array, element) {
  console.log('deleting '+element);
  const index = array.indexOf(element);
  array.splice(index, 1);
 }

但是结果不是我所期望的，结果如下：

Array(6) [ "apple", "orange", "watermelon", "blueberry", "lemon", "guava" ]
Array(5) [ "orange", "watermelon", "blueberry", "lemon", "guava" ]
Array(4) [ "orange", "blueberry", "lemon", "guava" ]

Answer 1

问题在于数组可迭代是 live -如果您使用for..of调用迭代器并在仍使用迭代器的同时对数组进行突变，迭代产生的结果可能很不直观-可能会遗漏某些指标。有点像这里发生的事情：

let items = ["apple", "orange", "watermelon", "blueberry", "lemon",   "guava"];
for (let i = 0; i < items.length; i++) {
  console.log('item: ', items[i]);
  items.splice(i, 1);
}

该循环仅运行3次，因为要在遍历数组的同时从数组中删除项目，因此跳过了一些指示。

一种可能性是，在使用for..of调用迭代器时，首先要复制数组，这样迭代器将始终按顺序遍历原始数组中的每个项目。：

let items = ["apple", "orange", "watermelon", "blueberry", "lemon",   "guava"];

runLoop = async () => {
  for(const item of items.slice()){
    await new Promise( resolve => setTimeout( resolve, 300 ));
    console.log(items);
    remove(items, item);
    console.log('------------');
  }
}

function remove(array, element) {
  console.log('deleting '+element);
  const index = array.indexOf(element);
  array.splice(index, 1);
}
runLoop();

Answer 2

您需要在索引零处拼接

array.splice(0, 1);

或仅移动第一个元素。

array.shift();

Answer 3

可以使用递归函数和shift来替代数组中的第一个元素

let items = ["apple", "orange", "watermelon", "blueberry", "lemon", "guava"];

function removeElem(arr) {
  if (arr.length !== 1) {
    console.log(arr)
    arr.shift();

    removeElem(arr)
  } else {
    console.log(arr)
  }
}
removeElem(items)

Answer 4

您可以使用Array.slice实现此目的。使用拼接时，请记住它将影响原始数组，根据javascript的功能方法，不应这样做。函数式编程不建议对原始对象进行变异。

let items = ["apple", "orange", "watermelon", "blueberry", "lemon", "guava"];

for(let i=0;i<items.length;i++){
   	console.log(items.slice(i,items.length));
 }

从第一个索引顺序删除数组javascript值

4 个答案: