Chrome扩展 - sendRequest缓慢

Question

我无法从我的后台脚本获取我的内容脚本请求值。

content_script.js 
================= 
var elements = undefined 
var properties = undefined 
var targets = undefined 
chrome.extension.sendRequest({greeting: "elements"}, function(response) { 
    elements = response.input; 
}); 
if (elements == undefined){ 
    var elements = ["a","img"]; 
}else{ 
    elements = elements.split(','); 
} 
chrome.extension.sendRequest({greeting: "properties"}, function(response) { 
    properties = response.input; 
}); 
if (properties == undefined){ 
    var properties = ["alt","id","class"]; 
}else{ 
    properties = properties.split(','); 
} 
chrome.extension.sendRequest({greeting: "targets"}, function(response) { 
    targets = response.input; 
}); 
if (targets == undefined){ 
    var targets = ["onclick","href"]; 
}else{ 
    targets = targets.split(','); 
}... 
...More code and references to elements following... 

上面的代码只有当在代码中休息做任何有关上述设定值之前（即等待）的作品，我想我可以把东西做到这一点，但我宁愿使用如果可能，更有效的解决方

（仅供参考:)

background.js 
============= 
chrome.extension.onRequest.addListener(
function(request, sender, sendResponse) { 
    switch (request.greeting){ 
     case "elements": 
       var elements = localStorage["elements"]; 
       sendResponse({input: elements}); 
       break; 
     case "properties": 
       var properties = localStorage["properties"]; 
       sendResponse({input: properties}); 
       break; 
     case "targets": 
       var targets = localStorage["targets"]; 
       sendResponse({input: targets}); 
       break; 
     } 
    }); 

我一直在这3小时（仍然在学习什么，我用JS做）

Answer 1

Uhhhhhm你不能做到这一点：

chrome.extension.sendRequest({greeting: "properties"}, function(response) { 
    properties = response.input; 
}); 
if (properties == undefined){ // always undefined 
    var properties = ["alt","id","class"]; 
}else{ 
    properties = properties.split(','); 
} 

sendRequest是异步的。

和检查未定义的正确的方法是：

if (typeof properties == "undefined") 

如果你需要所有的东西只是做1个请求并做回调里面所有的东西：

chrome.extension.sendRequest({greeting: "all"}, function(response) { 
    if (response.elements === null) { 
     var elements = ["a","img"]; 
    } else { 
     var elements = response.elements.split(','); 
    } 

    if (response.properties === null) { 
     var properties = ["alt","id","class"]; 
    } else { 
     var properties = response.properties.split(','); 
    } 

    if (response.targets === null) { 
     var targets = ["onclick","href"]; 
    } else { 
     var targets = response.targets.split(','); 
    } 
}); 

而在后台：

chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { 
    switch (request.greeting){ 
     case "all": 
      sendResponse({ 
       elements: localStorage.getItem("targets"), 
       properties: localStorage.getItem("properties"), 
       targets: localStorage.getItem("targets") 
      }); 
      break; 
    } 
});