在for循环迭代中删除数组时会发生什么？

Question

For example,

for (i in Cow.array){...}

If either Cow or Cow.array is removed, what will happen?

Also, if error occurs, how can I fix it?

Answer 1

Even this is will mostly not return in an error (so far you are using JavaScript - note that the last test results in an error) this will nearly always end up in strange behaviour:

 let myArr = [1,2,3,4] let myArr2 = [1,2,3,4] let myArr3 = [1,2,3,4] for (let i = 0; i < myArr.length; i++) { console.log("test without reomving: " + myArr[i]) } for (let i = 0; i < myArr.length; i++) { console.log("test with removing: " + myArr[i]) myArr.splice(i, 1); } for (let i = 0; i < myArr2.length; i++) { console.log("last test: " + myArr[i]) myArr2 = myArr2.splice(i, 1); } for (let i = 0; i < myArr3.length; i++) { console.log("very last test: " + myArr[i]) myArr3 = null } 

i strongly recommend NOT to do this

Answer 2

If your goal is to modify an array while looping on it. Try to avoid it as much as possible.

If you have to, use a copy of your array to iterate and modify your original array.

let myArray = [1, 2, 3, 4, 5]
let copy = myArray
for(let i=0; i<copy.length; i++) {
    //do stuff
    // for example remove number 3
    if(i == 3) {
        myArray.splice(i, 1);
    }
 }