13.AST遍历方式enter和exit的区别

AST抽象语法树/13.AST遍历方式enter和exit的区别/README.md

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+# AST遍历方式enter和exit的区别
+
+测试代码
+
+```javascript
+var a = 'a' + 'b' + 'c' + d + 'e' + 'f';
+```
+
+**默认的遍历方式enter**
+
+从代码结构的角度看，enter 钩子通常与深度优先遍历的进入节点的过程相对应，符合从上到下、从外到内的思维逻辑。
+
+```javascript
+const fs = require('fs');
+const {parse} = require("@babel/parser");
+const traverse = require("@babel/traverse").default;
+const generator = require("@babel/generator").default;
+const t = require('@babel/types');
+let encode_file = "./encode.js";
+
+let js_code = fs.readFileSync(encode_file, {encoding: "utf-8"});
+let ast = parse(js_code, {
+    sourceType: 'module',
+});
+
+
+const visitor = {
+    BinaryExpression(path){
+            console.log(path.toString())
+            const {confident, value} = path.evaluate();
+            confident && path.replaceWith(t.valueToNode(value));
+    },
+}
+
+traverse(ast, visitor);
+
+// 将修改后的AST重新生成为代码
+const modifiedCode = generator(ast).code;
+console.log(modifiedCode);
+```
+
+打印内容：
+
+    'a' + 'b' + 'c' + d + 'e' + 'f'
+    'a' + 'b' + 'c' + d + 'e'
+    'a' + 'b' + 'c' + d
+    'a' + 'b' + 'c'
+    var a = "abc" + d + 'e' + 'f';
+
+**exit遍历方式**
+
+从代码结构的角度看，exit 钩子通常与深度优先遍历的离开节点的过程相对应，符合从下到上、从内到外的思维逻辑。
+
+```javascript
+const fs = require('fs');
+const {parse} = require("@babel/parser");
+const traverse = require("@babel/traverse").default;
+const generator = require("@babel/generator").default;
+const t = require('@babel/types');
+let encode_file = "./encode.js";
+
+let js_code = fs.readFileSync(encode_file, {encoding: "utf-8"});
+let ast = parse(js_code, {
+    sourceType: 'module',
+});
+
+
+const visitor = {
+    BinaryExpression: {
+        exit: function(path) {
+            console.log(path.toString())
+            const {confident, value} = path.evaluate();
+            confident && path.replaceWith(t.valueToNode(value));
+        }
+    },
+}
+
+traverse(ast, visitor);
+
+// 将修改后的AST重新生成为代码
+const modifiedCode = generator(ast).code;
+console.log(modifiedCode);
+```
+
+打印内容：
+
+    'a' + 'b'
+    "ab" + 'c'
+    "abc" + d
+    "abc" + d + 'e'
+    "abc" + d + 'e' + 'f'
+    var a = "abc" + d + 'e' + 'f';

AST抽象语法树/13.AST遍历方式enter和exit的区别/decode_obfuscator.js

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+const fs = require('fs');
+const {parse} = require("@babel/parser");
+const traverse = require("@babel/traverse").default;
+const generator = require("@babel/generator").default;
+const t = require('@babel/types');
+let encode_file = "./encode.js";
+
+let js_code = fs.readFileSync(encode_file, {encoding: "utf-8"});
+let ast = parse(js_code, {
+    sourceType: 'module',
+});
+
+
+const visitor = {
+    BinaryExpression: {
+        exit: function(path) {
+            console.log(path.toString())
+            const {confident, value} = path.evaluate();
+            confident && path.replaceWith(t.valueToNode(value));
+        }
+    },
+}
+
+traverse(ast, visitor);
+
+// 将修改后的AST重新生成为代码
+const modifiedCode = generator(ast).code;
+console.log(modifiedCode);

AST抽象语法树/13.AST遍历方式enter和exit的区别/decode_obfuscator1.js

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+const fs = require('fs');
+const {parse} = require("@babel/parser");
+const traverse = require("@babel/traverse").default;
+const generator = require("@babel/generator").default;
+const t = require('@babel/types');
+let encode_file = "./encode.js";
+
+let js_code = fs.readFileSync(encode_file, {encoding: "utf-8"});
+let ast = parse(js_code, {
+    sourceType: 'module',
+});
+
+
+const visitor = {
+    BinaryExpression(path){
+            console.log(path.toString())
+            const {confident, value} = path.evaluate();
+            confident && path.replaceWith(t.valueToNode(value));
+    },
+}
+
+traverse(ast, visitor);
+
+// 将修改后的AST重新生成为代码
+const modifiedCode = generator(ast).code;
+console.log(modifiedCode);

AST抽象语法树/13.AST遍历方式enter和exit的区别/encode.js

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+var a = 'a' + 'b' + 'c' + d + 'e' + 'f';