javascriptの構文解析をしてみる ref: https://qiita.com/wicket/items/816c8703d23945462dfd

file0.txt

/**
 * comment
 */
function printTips() {
  var myHeading = document.querySelector('h1');
  myHeading.textContent = 'Hello world!';
}

file1.txt

{
  "type": "Program",
  "start": 0,
  "end": 135,
  "body": [
    {
      "type": "FunctionDeclaration",
      "start": 20,
      "end": 134,
      "id": {
        "type": "Identifier",
        "start": 29,
        "end": 38,
        "name": "printTips"
      },
      "generator": false,
      "expression": false,
      "params": [],
      "body": {
        "type": "BlockStatement",
        "start": 41,
        "end": 134,
        "body": [
          {
            "type": "VariableDeclaration",
            "start": 45,
            "end": 90,
            "declarations": [
              {
                "type": "VariableDeclarator",
                "start": 49,
                "end": 89,
                "id": {
                  "type": "Identifier",
                  "start": 49,
                  "end": 58,
                  "name": "myHeading"
                },
                "init": {
                  "type": "CallExpression",
                  "start": 61,
                  "end": 89,
                  "callee": {
                    "type": "MemberExpression",
                    "start": 61,
                    "end": 83,
                    "object": {
                      "type": "Identifier",
                      "start": 61,
                      "end": 69,
                      "name": "document"
                    },
                    "property": {
                      "type": "Identifier",
                      "start": 70,
                      "end": 83,
                      "name": "querySelector"
                    },
                    "computed": false
                  },
                  "arguments": [
                    {
                      "type": "Literal",
                      "start": 84,
                      "end": 88,
                      "value": "h1",
                      "raw": "'h1'"
                    }
                  ]
                }
              }
            ],
            "kind": "var"
          },
          {
            "type": "ExpressionStatement",
            "start": 93,
            "end": 132,
            "expression": {
              "type": "AssignmentExpression",
              "start": 93,
              "end": 131,
              "operator": "=",
              "left": {
                "type": "MemberExpression",
                "start": 93,
                "end": 114,
                "object": {
                  "type": "Identifier",
                  "start": 93,
                  "end": 102,
                  "name": "myHeading"
                },
                "property": {
                  "type": "Identifier",
                  "start": 103,
                  "end": 114,
                  "name": "textContent"
                },
                "computed": false
              },
              "right": {
                "type": "Literal",
                "start": 117,
                "end": 131,
                "value": "Hello world!",
                "raw": "'Hello world!'"
              }
            }
          }
        ]
      }
    }
  ],
  "sourceType": "module"
}

file2.txt

function printTips() {
  ...
}

file3.txt

{    
      "type": "FunctionDeclaration",
      "start": 20,
      "end": 134,
      "id": {
        "type": "Identifier",
        "start": 29,
        "end": 38,
        "name": "printTips"
      },
      "generator": false,
      "expression": false,
      "params": [],
      "body": {
           ...
      }
}

file4.txt

//  <script src="https://cdnjs.cloudflare.com/ajax/libs/acorn/5.5.3/acorn.js"></script>
//  <script src="https://cdnjs.cloudflare.com/ajax/libs/acorn/5.5.3/acorn_loose.js"></script>
//  <script src="https://cdnjs.cloudflare.com/ajax/libs/acorn/5.5.3/walk.js"></script>

let code = "...";
let ast;
try{
  ast = acorn.parse(code, {ecmaVersion: 8});  //構文解析をしてみる（パースできないとエラー）
}catch(err){
  ast = acorn.parse_dammit(code, {ecmaVersion: 8}); //構文解析をしてみる（パースできなくても無理やりパースしてエラーにならない）
}

function findAwaitKeyword(node, st, ancestors) {
   // ... 
}

acorn.walk.ancestor(ast, {
  AwaitExpression: findAwaitKeyword
});