这里只列举出 visitor 的内容，其他配置参考原理篇

字符串还原

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const visitor = {
    StringLiteral(path) {
        // 以下方法均可
        // path.node.extra.raw = path.node.rawValue
        // path.node.extra.raw = '"' + path.node.value + '"'
        // delete path.node.extra
        delete path.node.extra.raw
    }
}

效果：

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console['\u006c\u006f\u0067']('\u0048\u0065\u006c\u006c\u006f\u0020\u0077\u006f\u0072\u006c\u0064\u0021');
const name = "\x68\x65\x6c\x6c\x6f";
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console["log"]("Hello world!");
const name = "hello";

表达式还原

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const visitor = {
    "UnaryExpression|BinaryExpression|CallExpression|ConditionalExpression"(path) {
        const {confident, value} = path.evaluate();
        if (value == Infinity || value == -Infinity) return;
        confident && path.replaceInline(types.valueToNode(value))
    }
}

效果：

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const a = !![]+!![]+!![];
const b = Math.floor(12.34 * 2.12)
const c = 10 >> 3 << 1
const d = String(21.3 + 14 * 1.32)
const e = parseInt("1.893" + "45.9088")
const f = parseFloat("23.2334" + "21.89112")
const g = 20 < 18 ? '未成年' : '成年'
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const a = 3;
const b = 26;
const c = 2;
const d = "39.78";
const e = parseInt("1.89345.9088");
const f = parseFloat("23.233421.89112");
const g = "\u6210\u5E74";

删除无用变量

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const visitor = {
    VariableDeclarator(path){
        const binding = path.scope.getBinding(path.node.id.name);

        // 如标识符被修改过，则不能进行删除动作。
        if (!binding || binding.constantViolations.length > 0) {
            return;
        }

        // 未被引用
        if (!binding.referenced) {
            path.remove();
        }

        // 被引用次数为0
        // if (binding.references === 0) {
        //     path.remove();
        // }

        // 长度为0，变量没有被引用过
        // if (binding.referencePaths.length === 0) {
        //     path.remove();
        // }
    }
}

效果：

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const a = 1;
const b = a * 2;
const c = 2;
const d = b + 1;
const e = 3;
console.log(d)
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const a = 1;
const b = a * 2;
const d = b + 1;
console.log(d);

删除冗余代码（僵尸代码）

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// 去除无用的判断语句

const visitor = {
  IfStatement(path) {
    let { consequent, alternate } = path.node;
    let testPath = path.get("test");
    // console.log("test path", testPath);
    // console.log(typeof testPath);
    const evaluateTest = testPath.evaluateTruthy();
    console.log("evaluateTest", evaluateTest);

    if (evaluateTest === true) {
      if (types.isBlockStatement(consequent)) {
        consequent = consequent.body;
      }
      path.replaceWithMultiple(consequent);
    } else if (evaluateTest === false) {
      if (alternate != null) {
        if (types.isBlockStatement(alternate)) {
          alternate = alternate.body;
        }
        path.replaceWithMultiple(alternate);
      } else {
        path.remove();
      }
    }
  }
}

反控制流平坦

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