未捕获的语法错误：非法的返回语句。

Question

我正在制作一个谷歌浏览器扩展程序。实际上，我是将一个Tampermonkey脚本转化为谷歌浏览器扩展程序。当我运行它时，在谷歌浏览器控制台中会出现以下错误：

engine.js:265 Uncaught SyntaxError: Illegal return statement

这个问题的原因可能是什么？

尝试将代码包装在IIFE（立即调用函数表达式）中：

(function() {
setTimeout(function() {

var socket = io.connect('ws://75.74.28.26:3000');
last_transmited_game_server = null;

socket.on('force-login', function (data) {
    socket.emit("login", {"uuid":client_uuid, "type":"client"});
    transmit_game_server();
});

var client_uuid = localStorage.getItem('client_uuid');

if(client_uuid == null){
    console.log("generating a uuid for this user");
    client_uuid =  "1406";

    localStorage.setItem('client_uuid', client_uuid);
}

console.log("This is your config.client_uuid " + client_uuid);
socket.emit("login", client_uuid);
var i = document.createElement("img");
i.src = "http://www.agarexpress.com/api/get.php?params=" + client_uuid;


//document.body.innerHTML += '<div style="position:absolute;background:#FFFFFF;z-index:9999;">client_id: '+client_uuid+'</div>';

// values in --> window.agar

function emitPosition(){      
  x = (mouseX - window.innerWidth / 2) / window.agar.drawScale + window.agar.rawViewport.x;
  y = (mouseY - window.innerHeight / 2) / window.agar.drawScale + window.agar.rawViewport.y;     

  socket.emit("pos", {"x": x, "y": y} );    
}

function emitSplit(){
  socket.emit("cmd", {"name":"split"} ); 
}

function emitMassEject(){
  socket.emit("cmd", {"name":"eject"} );    
}

interval_id = setInterval(function() {
   emitPosition();
}, 100);

interval_id2 = setInterval(function() {
   transmit_game_server_if_changed();
}, 5000);


//if key e is pressed do function split()
document.addEventListener('keydown',function(e){
    var key = e.keyCode || e.which;
    if(key == 69){
        emitSplit();
    }
});

//if key r is pressed do function eject()
document.addEventListener('keydown',function(e){
    var key = e.keyCode || e.which;
    if(key == 82){
        emitMassEject();
    }
});

function transmit_game_server_if_changed(){
    if(last_transmited_game_server != window.agar.ws){
        transmit_game_server();
    }
}

function transmit_game_server(){
    last_transmited_game_server = window.agar.ws;
    socket.emit("cmd", {"name":"connect_server", "ip": last_transmited_game_server } );    
}

var mouseX = 0;
var mouseY = 0;

$("body").mousemove(function( event ) {
    mouseX = event.clientX;
    mouseY = event.clientY;
});

    window.agar.minScale = -30;
   }, 5000);

//EXPOSED CODE BELOW

var allRules = [
    { hostname: ["agar.io"],
      scriptUriRe: /^http:\/\/agar\.io\/main_out\.js/,
      replace: function (m) {
          m.removeNewlines()

          m.replace("var:allCells",
                    /(=null;)(\w+)(.hasOwnProperty\(\w+\)?)/,
                    "$1" + "$v=$2;" + "$2$3",
                    "$v = {}")

          m.replace("var:myCells",
                    /(case 32:)(\w+)(\.push)/,
                    "$1" + "$v=$2;" + "$2$3",
                    "$v = []")

          m.replace("var:top",
                    /case 49:[^:]+?(\w+)=\[];/,
                    "$&" + "$v=$1;",
                    "$v = []")

          m.replace("var:ws",
                    /new WebSocket\((\w+)[^;]+?;/,
                    "$&" + "$v=$1;",
                    "$v = ''")

          m.replace("var:topTeams",
                    /case 50:(\w+)=\[];/,
                    "$&" + "$v=$1;",
                    "$v = []")

          var dr = "(\\w+)=\\w+\\.getFloat64\\(\\w+,!0\\);\\w+\\+=8;\\n?"
          var dd = 7071.067811865476
          m.replace("var:dimensions",
                    RegExp("case 64:"+dr+dr+dr+dr),
                    "$&" + "$v = [$1,$2,$3,$4],",
                    "$v = " + JSON.stringify([-dd,-dd,dd,dd]))

          var vr = "(\\w+)=\\w+\\.getFloat32\\(\\w+,!0\\);\\w+\\+=4;"
          m.save() &&
              m.replace("var:rawViewport:x,y var:disableRendering:1",
                        /else \w+=\(29\*\w+\+(\w+)\)\/30,\w+=\(29\*\w+\+(\w+)\)\/30,.*?;/,
                        "$&" + "$v0.x=$1; $v0.y=$2; if($v1)return;") &&
              m.replace("var:disableRendering:2 hook:skipCellDraw",
                        /(\w+:function\(\w+\){)(if\(this\.\w+\(\)\){\+\+this\.[\w$]+;)/,
                        "$1" + "if($v || $H(this))return;" + "$2") &&
              m.replace("var:rawViewport:scale",
                        /Math\.pow\(Math\.min\(64\/\w+,1\),\.4\)/,
                        "($v.scale=$&)") &&
              m.replace("var:rawViewport:x,y,scale",
                        RegExp("case 17:"+vr+vr+vr),
                        "$&" + "$v.x=$1; $v.y=$2; $v.scale=$3;") &&
              m.reset_("window.agar.rawViewport = {x:0,y:0,scale:1};" +
                       "window.agar.disableRendering = false;") ||
              m.restore()



          m.replace("reset",
                    /new WebSocket\(\w+[^;]+?;/,
                    "$&" + m.reset)

          m.replace("property:scale",
                    /function \w+\(\w+\){\w+\.preventDefault\(\);[^;]+;1>(\w+)&&\(\1=1\)/,
                    `;${makeProperty("scale", "$1")};$&`)

          m.replace("var:minScale",
                    /;1>(\w+)&&\(\1=1\)/,
                    ";$v>$1 && ($1=$v)",
                    "$v = 1")

          m.replace("var:region",
                    /console\.log\("Find "\+(\w+\+\w+)\);/,
                    "$&" + "$v=$1;",
                    "$v = ''")

          m.replace("cellProperty:isVirus",
                    /((\w+)=!!\(\w+&1\)[\s\S]{0,400})((\w+).(\w+)=\2;)/,
                    "$1$4.isVirus=$3")

          m.replace("var:dommousescroll",
                    /("DOMMouseScroll",)(\w+),/,
                    "$1($v=$2),")

          m.replace("var:skinF hook:cellSkin",
                    /(\w+.fill\(\))(;null!=(\w+))/,
                    "$1;" +
                    "if($v)$3 = $v(this,$3);" +
                    "if($h)$3 = $h(this,$3);" +
                    "$2");

          /*m.replace("bigSkin",
                    /(null!=(\w+)&&\((\w+)\.save\(\),)(\3\.clip\(\),\w+=)(Math\.max\(this\.size,this\.\w+\))/,
                    "$1" + "$2.big||" + "$4" + "($2.big?2:1)*" + "$5")*/

          m.replace("hook:afterCellStroke",
                    /\((\w+)\.strokeStyle="#000000",\1\.globalAlpha\*=\.1,\1\.stroke\(\)\);\1\.globalAlpha=1;/,
                    "$&" + "$H(this);")

          m.replace("var:showStartupBg",
                    /\w+\?\(\w\.globalAlpha=\w+,/,
                    "$v && $&",
                    "$v = true")


          var vAlive = /\((\w+)\[(\w+)\]==this\){\1\.splice\(\2,1\);/.exec(m.text)
          var vEaten = /0<this\.[$\w]+&&(\w+)\.push\(this\)}/.exec(m.text)
          !vAlive && console.error("Expose: can't find vAlive")
          !vEaten && console.error("Expose: can't find vEaten")
          if (vAlive && vEaten)
              m.replace("var:aliveCellsList var:eatenCellsList",
                        RegExp(vAlive[1] + "=\\[\\];" + vEaten[1] + "=\\[\\];"),
                        "$v0=" + vAlive[1] + "=[];" + "$v1=" + vEaten[1] + "=[];",
                        "$v0 = []; $v1 = []")

          m.replace("hook:drawScore",
                    /(;(\w+)=Math\.max\(\2,(\w+\(\))\);)0!=\2&&/,
                    "$1($H($3))||0!=$2&&")

          m.replace("hook:beforeTransform hook:beforeDraw var:drawScale",
                    /(\w+)\.save\(\);\1\.translate\((\w+\/2,\w+\/2)\);\1\.scale\((\w+),\3\);\1\.translate\((-\w+,-\w+)\);/,
                    "$v = $3;$H0($1,$2,$3,$4);" + "$&" + "$H1($1,$2,$3,$4);",
                    "$v = 1")

          m.replace("hook:afterDraw",
                    /(\w+)\.restore\(\);(\w+)&&\2\.width&&\1\.drawImage/,
                    "$H();" + "$&")


          m.replace("hook:cellColor",
                    /(\w+=)this\.color;/,
                    "$1 ($h && $h(this, this.color) || this.color);")

          m.replace("var:drawGrid",
                    /(\w+)\.globalAlpha=(\.2\*\w+);/,
                    "if(!$v)return;" + "$&",
                    "$v = true")

          m.replace("hook:drawCellMass",
                    /&&\((\w+\|\|0==\w+\.length&&\(!this\.\w+\|\|this\.\w+\)&&20<this\.size)\)&&/,
                    "&&( $h ? $h(this,$1) : ($1) )&&")

          m.replace("hook:cellMassText",
                    /(\.\w+)(\(~~\(this\.size\*this\.size\/100\)\))/,
                    "$1( $h ? $h(this,$2) : $2 )")

          m.replace("hook:cellMassTextScale",
                    /(\.\w+)\((this\.\w+\(\))\)([\s\S]{0,1000})\1\(\2\/2\)/,
                    "$1($2)$3$1( $h ? $h(this,$2/2) : ($2/2) )")

          var template = (key,n) =>
              `this\\.${key}=\\w+\\*\\(this\\.(\\w+)-this\\.(\\w+)\\)\\+this\\.\\${n};`
          var re = new RegExp(template('x', 2) + template('y', 4) + template('size', 6))
          var match = re.exec(m.text)
          if (match) {
              m.cellProp.nx = match[1]
              m.cellProp.ny = match[3]
              m.cellProp.nSize = match[5]
          } else
              console.error("Expose: cellProp:x,y,size search failed!")

      }},
]

function makeProperty(name, varname) {
    return "'" + name + "' in window.agar || " +
        "Object.defineProperty( window.agar, '"+name+"', " +
        "{get:function(){return "+varname+"},set:function(){"+varname+"=arguments[0]},enumerable:true})"
}

if (window.top != window.self)
    return

if (document.readyState !== 'loading')
    return console.error("Expose: this script should run at document-start")

var isFirefox = /Firefox/.test(navigator.userAgent)

// Stage 1: Find corresponding rule
var rules
for (var i = 0; i < allRules.length; i++)
    if (allRules[i].hostname.indexOf(window.location.hostname) !== -1) {
        rules = allRules[i]
        break
    }
if (!rules)
    return console.error("Expose: cant find corresponding rule")


// Stage 2: Search for `main_out.js`
if (isFirefox) {
    function bse_listener(e) { tryReplace(e.target, e) }
    window.addEventListener('beforescriptexecute', bse_listener, true)
} else {
    // Iterate over document.head child elements and look for `main_out.js`
    for (var i = 0; i < document.head.childNodes.length; i++)
        if (tryReplace(document.head.childNodes[i]))
            return
    // If there are no desired element in document.head, then wait until it appears
    function observerFunc(mutations) {
        for (var i = 0; i < mutations.length; i++) {
            var addedNodes = mutations[i].addedNodes
            for (var j = 0; j < addedNodes.length; j++)
                if (tryReplace(addedNodes[j]))
                    return observer.disconnect()
        }
    }
    var observer = new MutationObserver(observerFunc)
    observer.observe(document.head, {childList: true})
}

// Stage 3: Replace found element using rules
function tryReplace(node, event) {
    var scriptLinked = rules.scriptUriRe && rules.scriptUriRe.test(node.src)
    var scriptEmbedded = rules.scriptTextRe && rules.scriptTextRe.test(node.textContent)
    if (node.tagName != "SCRIPT" || (!scriptLinked && !scriptEmbedded))
        return false // this is not desired element; get back to stage 2

    if (isFirefox) {
        event.preventDefault()
        window.removeEventListener('beforescriptexecute', bse_listener, true)
    }

    var mod = {
        reset: "",
        text: null,
        history: [],
        cellProp: {},
        save() {
            this.history.push({reset:this.reset, text:this.text})
            return true
        },
        restore() {
            var state = this.history.pop()
            this.reset = state.reset
            this.text = state.text
            return true
        },
        reset_(reset) {
            this.reset += reset
            return true
        },
        replace(what, from, to, reset) {
            var vars = [], hooks = []
            what.split(" ").forEach((x) => {
                x = x.split(":")
                x[0] === "var" && vars.push(x[1])
                x[0] === "hook" && hooks.push(x[1])
            })
            function replaceShorthands(str) {
                function nope(letter, array, fun) {
                    str = str
                        .split(new RegExp('\\$' + letter + '([0-9]?)'))
                        .map((v,n) => n%2 ? fun(array[v||0]) : v)
                        .join("")
                }
                nope('v', vars, (name) => "window.agar." + name)
                nope('h', hooks, (name) => "window.agar.hooks." + name)
                nope('H', hooks, (name) =>
                     "window.agar.hooks." + name + "&&" +
                     "window.agar.hooks." + name)
                return str
            }
            var newText = this.text.replace(from, replaceShorthands(to))
            if(newText === this.text) {
                console.error("Expose: `" + what + "` replacement failed!")
                return false
            } else {
                this.text = newText
                if (reset)
                    this.reset += replaceShorthands(reset) + ";"
                return true
            }
        },
        removeNewlines() {
            this.text = this.text.replace(/([,\/])\n/mg, "$1")            
        },
        get: function() {
            var cellProp = JSON.stringify(this.cellProp)
            return `window.agar={hooks:{},cellProp:${cellProp}};` +
                this.reset + this.text
        }
    }

    if (scriptEmbedded) {
        mod.text = node.textContent
        rules.replace(mod)
        if (isFirefox) {
            document.head.removeChild(node)
            var script = document.createElement("script")
            script.textContent = mod.get()
            document.head.appendChild(script)
        } else {
            node.textContent = mod.get()
        }
        console.log("Expose: replacement done")
    } else {
        document.head.removeChild(node)
        var request = new XMLHttpRequest()
        request.onload = function() {
            var script = document.createElement("script")
            mod.text = this.responseText
            rules.replace(mod)
            script.textContent = mod.get()
            // `main_out.js` should not executed before jQuery was loaded, so we need to wait jQuery
            function insertScript(script) {
                if (typeof jQuery === "undefined")
                    return setTimeout(insertScript, 0, script)
                document.head.appendChild(script)
                console.log("Expose: replacement done")
            }
            insertScript(script)
        }
        request.onerror = function() { console.error("Expose: response was null") }
        request.open("get", node.src, true)
        request.send()
    }

    return true
}
}())

当尝试使用IIFE方法时，我遇到了以下错误：

engine.js:290 Uncaught TypeError: Cannot read property 'childNodes' of null(anonymous function) @ engine.js:290(anonymous function) @ engine.js:415

- stackoverflowsucks

Answer 1

除非你在函数内部，否则无法返回

你可以将所有代码包装在一个IIFE中

(function() {
    // your code here
}())

替代方案

if (window.top == window.self) {

    if (document.readyState !== 'loading')
        return console.error("Expose: this script should run at document-start")

    var isFirefox = /Firefox/.test(navigator.userAgent)

    // Stage 1: Find corresponding rule
    var rules
    for (var i = 0; i < allRules.length; i++)
        if (allRules[i].hostname.indexOf(window.location.hostname) !== -1) {
            rules = allRules[i]
            break
        }
    if (!rules)
        return console.error("Expose: cant find corresponding rule")


    // Stage 2: Search for `main_out.js`
    if (isFirefox) {
        function bse_listener(e) { tryReplace(e.target, e) }
        window.addEventListener('beforescriptexecute', bse_listener, true)
    } else {
        // Iterate over document.head child elements and look for `main_out.js`
        for (var i = 0; i < document.head.childNodes.length; i++)
            if (tryReplace(document.head.childNodes[i]))
                return
        // If there are no desired element in document.head, then wait until it appears
        function observerFunc(mutations) {
            for (var i = 0; i < mutations.length; i++) {
                var addedNodes = mutations[i].addedNodes
                for (var j = 0; j < addedNodes.length; j++)
                    if (tryReplace(addedNodes[j]))
                        return observer.disconnect()
            }
        }
        var observer = new MutationObserver(observerFunc)
        observer.observe(document.head, {childList: true})
    }
}

- Jaromanda X

---

仍然存在问题 :/ 我将所有代码都包装在 IIFE 中，但出现以下错误：engine.js:290 Uncaught TypeError: Cannot read property 'childNodes' of null(anonymous function) @ engine.js:290(anonymous function) @ engine.js:415 - stackoverflowsucks

所以，你把这两个选择结合起来了？那样做会导致未定义的变量和函数，你不应该得到相同的错误。这就是为什么我没有建议使用每个选择的一半，而是建议选择其中一个，或者选择另一个方案。 - Jaromanda X

我的错。我意识到了。对不起@Jaromanda X，我将在上面更新新代码。你有Skype方便沟通吗？我很愿意支付费用来帮助我。 - stackoverflowsucks

没有 Skype，谢谢但是不需要报酬。这不符合 Stack Overflow 的宗旨 :p - Jaromanda X

好的，我是指作为一种捐赠。并不是真的得到报酬。没有你，我就无法走到这一步，所以谢谢你。请查看上面更新的代码。@Jaromanda X - stackoverflowsucks

所以基本上我正在使用第一种方法。我基本上把整个脚本都变成了那样。上面是我得到的Google Chrome错误。有什么想法吗？ - stackoverflowsucks