js如何实现文本差异对比 4种差异比对算法快速找出文本变化内容

function lcs(str1, str2) {
  const m = str1.length;
  const n = str2.length;
  const dp = Array(m + 1).fill(null).map(() => Array(n + 1).fill(0));

  for (let i = 1; i <= m; i++) {
    for (let j = 1; j <= n; j++) {
      if (str1[i - 1] === str2[j - 1]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
      } else {
        dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
      }
    }
  }

  // 回溯找到LCS
  let i = m, j = n;
  let lcsStr = "";
  while (i > 0 && j > 0) {
    if (str1[i - 1] === str2[j - 1]) {
      lcsStr = str1[i - 1] + lcsStr;
      i--;
      j--;
    } else if (dp[i - 1][j] > dp[i][j - 1]) {
      i--;
    } else {
      j--;
    }
  }

  return lcsStr;
}

// 示例
const str1 = "ABCBDAB";
const str2 = "BDCABA";
const result = lcs(str1, str2);
console.log("LCS:", result); // 输出: LCS: BCBA

// 使用 jsdiff 库
const jsdiff = require('diff');

const str1 = "This is a sentence.";
const str2 = "This is another sentence.";

const diff = jsdiff.diffChars(str1, str2);

diff.forEach((part) => {
  const color = part.added ? 'green' :
                part.removed ? 'red' : 'grey';
  process.stderr.write(part.value[color]);
});
console.log();

function levenshteinDistance(str1, str2) {
  const m = str1.length;
  const n = str2.length;
  const dp = Array(m + 1).fill(null).map(() => Array(n + 1).fill(0));

  for (let i = 0; i <= m; i++) {
    dp[i][0] = i;
  }
  for (let j = 0; j <= n; j++) {
    dp[0][j] = j;
  }

  for (let i = 1; i <= m; i++) {
    for (let j = 1; j <= n; j++) {
      if (str1[i - 1] === str2[j - 1]) {
        dp[i][j] = dp[i - 1][j - 1];
      } else {
        dp[i][j] = Math.min(
          dp[i - 1][j] + 1, // 删除
          dp[i][j - 1] + 1, // 插入
          dp[i - 1][j - 1] + 1 // 替换
        );
      }
    }
  }

  return dp[m][n];
}

// 示例
const str1 = "kitten";
const str2 = "sitting";
const distance = levenshteinDistance(str1, str2);
console.log("Levenshtein Distance:", distance); // 输出: Levenshtein Distance: 3

function wordDiff(str1, str2) {
  const words1 = str1.split(/\s+/);
  const words2 = str2.split(/\s+/);

  // 简单的比较，可以根据需要使用更复杂的算法
  const added = words2.filter(word => !words1.includes(word));
  const removed = words1.filter(word => !words2.includes(word));

  return { added, removed };
}

// 示例
const str1 = "This is a simple example.";
const str2 = "This is another simple example.";

const diff = wordDiff(str1, str2);
console.log("Added:", diff.added);   // 输出: Added: [ 'another' ]
console.log("Removed:", diff.removed); // 输出: Removed: [ 'a' ]