146 lines
3.2 KiB
Markdown
146 lines
3.2 KiB
Markdown
# 数组与字符串操作
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## 1. 数组去重（多种方法）
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```js
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// 方法1: Set
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const unique1 = arr => [...new Set(arr)];
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// 方法2: filter + indexOf
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const unique2 = arr => arr.filter((v, i) => arr.indexOf(v) === i);
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// 方法3: reduce
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const unique3 = arr => arr.reduce((acc, v) => acc.includes(v) ? acc : [...acc, v], []);
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// 方法4: 对象数组按属性去重
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const uniqueByKey = (arr, key) => {
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const map = new Map();
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arr.forEach(item => !map.has(item[key]) && map.set(item[key], item));
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return [...map.values()];
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};
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```
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## 2. 扁平化数组
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```js
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// 递归实现
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function flatten(arr, depth = Infinity) {
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return arr.reduce((acc, val) => {
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return acc.concat(
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Array.isArray(val) && depth > 0 ? flatten(val, depth - 1) : val
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);
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}, []);
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}
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// 迭代实现（使用栈）
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function flattenIterative(arr) {
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const stack = [...arr];
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const result = [];
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while (stack.length) {
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const item = stack.pop();
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Array.isArray(item) ? stack.push(...item) : result.unshift(item);
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}
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return result;
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}
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// 原生方法
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arr.flat(Infinity);
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```
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## 3. 字符串反转
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```js
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const reverse = str => str.split('').reverse().join('');
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// 或者使用扩展运算符
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const reverse2 = str => [...str].reverse().join('');
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```
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## 4. 判断回文
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```js
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const isPalindrome = str => {
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const clean = str.toLowerCase().replace(/[^a-z0-9]/g, '');
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return clean === clean.split('').reverse().join('');
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};
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// 双指针法
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const isPalindrome2 = str => {
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const s = str.toLowerCase().replace(/[^a-z0-9]/g, '');
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let left = 0, right = s.length - 1;
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while (left < right) {
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if (s[left++] !== s[right--]) return false;
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}
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return true;
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};
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```
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## 5. 最长公共前缀
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```js
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function longestCommonPrefix(strs) {
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if (!strs.length) return '';
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let prefix = strs[0];
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for (let i = 1; i < strs.length; i++) {
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while (strs[i].indexOf(prefix) !== 0) {
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prefix = prefix.slice(0, -1);
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if (!prefix) return '';
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}
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}
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return prefix;
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}
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// 示例: ["flower","flow","flight"] => "fl"
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```
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## 6. 模板字符串解析
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```js
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function render(template, data) {
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return template.replace(/\{\{(\w+)\}\}/g, (match, key) => {
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return data[key] !== undefined ? data[key] : match;
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});
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}
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// 支持嵌套属性
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function renderDeep(template, data) {
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return template.replace(/\{\{(.+?)\}\}/g, (match, path) => {
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const keys = path.trim().split('.');
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let value = data;
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for (const key of keys) {
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value = value?.[key];
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if (value === undefined) return match;
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}
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return value;
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});
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}
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// 使用示例
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render('Hello, {{name}}!', { name: 'World' }); // "Hello, World!"
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renderDeep('{{user.info.name}}', { user: { info: { name: 'Tom' } } }); // "Tom"
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```
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## 7. 数组按属性去重并排序
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```js
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function uniqueAndSort(arr, key, sortKey, order = 'asc') {
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// 去重
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const map = new Map();
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arr.forEach(item => !map.has(item[key]) && map.set(item[key], item));
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// 排序
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return [...map.values()].sort((a, b) => {
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return order === 'asc' ? a[sortKey] - b[sortKey] : b[sortKey] - a[sortKey];
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});
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}
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// 示例
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const users = [
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{ id: 1, name: 'Tom', age: 20 },
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{ id: 2, name: 'Jerry', age: 18 },
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{ id: 1, name: 'Tom2', age: 25 }
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];
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uniqueAndSort(users, 'id', 'age'); // 按id去重，按age升序排序
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```
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