实现简单版的手写数组 API，后续更新完整版。
at
Array.prototype._at = function (index) {
index = index < 0 ? index + this.length : index;
if (index > this.length - 1 || index < 0) {
return Error('index 取值错误');
}
return this[index];
};
concat
Array.prototype._concat = function (...valueN) {
return [...this.slice(), ...valueN.flat()];
};
every
Array.prototype._every = function (callback, thisArg) {
for (let i = 0; i < this.length; i++) {
if (!callback.call(thisArg, this[i], i, this)) {
return false;
}
}
return true;
};
fill
Array.prototype._fill = function (value, start, end) {
start = start || Number.isNaN(start) ? start : 0;
end = end || Number.isNaN(start) ? end : this.length;
if (isNaN(start)) {
return this;
}
if (start > this.length) {
return this;
}
if (start < 0) {
start = start + this.length;
}
if (end < 0) {
end = end + this.length;
}
if (end > this.length) {
end = this.length;
}
for (let i = start; i < end; i++) {
this[i] = value;
}
return this;
};
filter
Array.prototype._filter = function (callback, thisArg) {
let result = [];
for (let i = 0; i < this.length; i++) {
if (callback.call(thisArg, this[i], i, this)) {
result.push(this[i]);
}
}
return result;
};
find
Array.prototype._find = function (callback, thisArg) {
for (let i = 0; i < this.length; i++) {
if (callback.call(thisArg, this[i], i, this)) {
return this[i];
}
}
};
findIndex
Array.prototype._findIndex = function (callback, thisArg) {
for (let i = 0; i < this.length; i++) {
if (callback.call(thisArg, this[i], i, this)) {
return i;
}
}
return -1;
};
flat
Array.prototype._flat = function (depth = 1) {
function isArray(param) {
return Object.prototype.toString.call(param).slice(8, -1) === 'Array';
}
const result = [];
this.forEach(item => {
if (isArray(item)) {
if (depth > 0) {
result.push(...item._flat(depth - 1));
} else {
result.push(item);
}
} else {
result.push(item);
}
});
return result;
};
forEach
Array.prototype._forEach = function (callback, thisArg) {
const len = this.length;
for (let i = 0; i < len; i++) {
callback.call(thisArg, this[i], i, this);
}
};
includes
Array.prototype._includes = function (valueToFind, fromIndex) {
fromIndex = fromIndex ? (fromIndex < 0 ? fromIndex + this.length : fromIndex) : 0;
for (let i = fromIndex; i < this.length; i++) {
if (valueToFind === this[i] || (valueToFind !== valueToFind && this[i] !== this[i])) {
return true;
}
}
return false;
};
indexOf
Array.prototype._indexOf = function (searchElement, fromIndex) {
fromIndex = fromIndex ? fromIndex : 0;
if (fromIndex > this.length) {
return -1;
}
if (fromIndex < 0) {
fromIndex = this.length + fromIndex;
if (fromIndex < 0) {
fromIndex = 0;
}
}
let index = fromIndex;
while (index < this.length) {
if (this[index] === searchElement) {
return index;
}
index++;
}
return -1;
};
isArray
function isArray(param) {
return Object.prototype.toString.call(param).slice(8, -1) === 'Array';
}
join
Array.prototype._join = function (separator) {
separator = separator ? separator : ',';
let result = '';
for (let i = 0; i < this.length; i++) {
result += `${this[i]}${separator}`;
}
return result.slice(0, -1);
};
lastIndexOf
Array.prototype._lastIndexOf = function (searchElement, fromIndex) {
fromIndex = fromIndex ? fromIndex : this.length;
if (fromIndex > this.length) {
return -1;
}
if (fromIndex < 0) {
fromIndex = this.length + fromIndex;
if (fromIndex < 0) {
fromIndex = 0;
}
}
let index = fromIndex;
while (index >= 0) {
if (this[index] === searchElement) {
return index;
}
index--;
}
return -1;
};
map
Array.prototype._map = function (callback, context) {
let result = [];
const context = context ? context : this;
this.forEach((item, index) => {
result.push(callback.call(context, item, index, me));
});
return result;
};
pop
Array.prototype._pop = function () {
if (!this.length) {
return undefined;
}
const delItem = this[this.length - 1];
this.length = this.length - 1;
return delItem;
};
push
Array.prototype._push = function (...elementList) {
for (let i = 0; i < elementList.length; i++) {
this[this.length + i] = elementList[i];
}
return this.length;
};
reduce
Array.prototype._reduce = function (callback, initialValue) {
let i = initialValue ? 0 : 1;
let result = initialValue ? initialValue : this[0];
for (; i < this.length; i++) {
result = callback(result, this[i], i, this);
}
return result;
};
reverse
Array.prototype._reverse = function () {
let left = 0;
let right = this.length - 1;
let temp;
while (left < right) {
temp = this[left];
this[left] = this[right];
this[right] = temp;
left++;
right--;
}
return this;
};
shift
Array.prototype._shift = function () {
if (!this.length) {
return undefined;
}
const returnItem = this[0];
for (let i = 1; i < this.length; i++) {
this[i - 1] = this[i];
}
this.length = this.length - 1;
return returnItem;
};
slice
Array.prototype._slice = function (start, end) {
const res = [];
const { length } = this;
if (start < 0) {
start += length;
if (start < 0) {
start = 0;
}
} else {
if (start > length) {
start = length;
}
}
if (end < 0) {
end += length;
if (end < 0) {
end = 0;
}
} else {
if (end > length) {
end = length;
}
}
for (let i = start; i < end; i++) {
res.push(this[i]);
}
return res;
};
some
Array.prototype._some = function (fn, ctx) {
for (let i = 0; i < this.length; i++) {
if (fn.call(ctx, this[i], i, this)) {
return true;
}
}
return false;
};
splice
Array.prototype._splice = function (start, deleteCount, ...items) {
let { length } = this;
start = start || start === 0 ? start : 0;
if (start < 0) {
start = start + length;
if (start < 0) {
start = 0;
}
} else {
if (start > length) {
start = length;
}
}
deleteCount = deleteCount || deleteCount === 0 ? deleteCount : length - start;
if (deleteCount + start > length) {
deleteCount = length;
}
if (deleteCount < 0) {
deleteCount = 0;
}
const remainList = this.slice(start + deleteCount);
const deletedItemList = this.slice(start, start + deleteCount);
for (let i = 0; i < items.length; i++) {
this[start + i] = items[i];
}
for (let i = 0; i < remainList.length; i++) {
this[start + items.length + i] = remainList[i];
}
this.length = length - deleteCount + items.length;
return deletedItemList;
};
toString
Array.prototype._toString = function () {
let res = '';
for (let i = 0; i < this.length - 1; i++) {
res += `${this[i] },`;
}
res += this[this.length - 1];
return res;
};
unshift
Array.prototype._unshift = function (...unshiftItemList) {
for (let i = this.length - 1 + unshiftItemList.length; i > this.length - 1 - unshiftItemList.length; i--) {
this[i] = this[i - unshiftItemList.length];
}
for (let i = 0; i < unshiftItemList.length; i++) {
this[i] = unshiftItemList[i];
}
return this.length;
};
