移动元素函数里 判断over<0的情况 i应该从startIdx+delCount+over开始

[xllpiupiu]

移动元素函数里 判断over<0的情况 i应该从startIdx+delCount+over开始
/**
数组splice方法实现

arr.splice(startIdx,delCount,add1,add2,...);
*/
Array.prototype._splice = function () {
//1. 记录入参个数
let argumentsLen = arguments.length;
let start = arguments[0], deleteCount = arguments[1];
//2. 数组长度
let arrayLength = this.length;
let arr = Object(this);
//3. 添加元素个数
let addCount = argumentsLen > 2 ? argumentsLen - 2 : 0
console.log('addCount: ', addCount);
//4. 计算有效的开始位置start
let startIdx = computeSpliceStartIdx(start, arrayLength);
//5. 计算有效的删除个数
let delCount = computeSpiceDelCount(startIdx, deleteCount, arrayLength);

console.log('delCount: ', delCount);
//6. 记录删除的元素
let delElements = new Array(delCount);
recordDelElements(startIdx, delCount, arr, delElements);
//7. 判断是否是密封对象
if (delCount !== addCount && Object.isSealed(arr)) {
throw new TypeError('the arr is sealed')
}
//8. 判断是否是冻结对象
if (delCount > 0 && addCount > 0 && Object.isFrozen(arr)) {
throw new TypeError('the arr is frozen')
}
//移动数组元素
moveElements(startIdx, delCount, arr, addCount);
let i = startIdx;
let argumentsIdx = 2;
//插入新的元素
while (argumentsIdx < argumentsLen) {
arr[i++] = arguments[argumentsIdx++];
}
arr.length = arrayLength - delCount + addCount;
return delElements;
}
function computeSpliceStartIdx(start, arrayLength) {
if (start < 0) {
start += arrayLength;
return start < 0 ? 0 : start;
}
//start>0的情况
return start > arrayLength - 1 ? arrayLength - 1 : start;
}
//计算delCount
function computeSpiceDelCount(startIdx, deleteCount, arrayLength) {
if (deleteCount > arrayLength - startIdx) {
deleteCount = arrayLength - startIdx
}
if (deleteCount < 0) deleteCount = 0
return deleteCount;
}
//记录删除的元素
function recordDelElements(startIdx,delCount,arr,delElements) {
for(let i=0;i<delCount;i++) {
delElements[i] = arr[startIdx+i];
}
}
//移动数组
function moveElements(startIdx, delCount, arr, addCount){
let over = addCount - delCount;
console.log('over: ', over);
if(over>0) {
//增加的数大于了删除的数 向后移动
for(let i=arr.length-1;i>=startIdx+delCount;i--) {
arr[i+over] = arr[i];
}
} else if(over<0) {
//增加的数小于删除的数 向前移动
for(let i=startIdx+delCount+over;i<=arr.length-1;i++) {
if(i+Math.abs(over)>arr.length-1) {
delete arr[i]
continue
}
arr[i] = arr[i+Math.abs(over)];
}
console.log('arr: over<0', arr);
}
}
let arr = [1, 2, 3, 4, 5];
arr._splice(1,3,6,7)
console.log('arr: ', arr);//arr: [ 1, 6, 7, 5 ]

Originally posted by @xllpiupiu in #138 (comment)