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Javascript 从异步表达式中获取返回值_Javascript_Node.js - Fatal编程技术网

Javascript 从异步表达式中获取返回值

Javascript 从异步表达式中获取返回值,javascript,node.js,Javascript,Node.js,如何从以下代码中获取返回值?我不想只是把它记录下来 function get_disk_space(callback){ checkDiskSpace('C:\\').then((diskSpace) => { var free = Math.floor(diskSpace.free/1000000000) var size = Math.floor(diskSpace.size/1000000000) var used = size - fre

如何从以下代码中获取返回值?我不想只是把它记录下来

function get_disk_space(callback){
    checkDiskSpace('C:\\').then((diskSpace) => {
      var free = Math.floor(diskSpace.free/1000000000)
      var size = Math.floor(diskSpace.size/1000000000)
      var used = size - free
      percent = (size - free)
      percent = percent/size*100
      percent = Math.floor(percent)+'%'
      return percent;
    });
  }

在返回百分比之前运行控制台日志时,运行此命令将返回未定义的值。您只需添加一个
,然后添加一个
-处理程序来处理已解析的值,例如:

function get_disk_space(callback) {
    return checkDiskSpace('C:\\').then((diskSpace) => {
        var free = Math.floor(diskSpace.free / 1000000000)
        var size = Math.floor(diskSpace.size / 1000000000)
        var used = size - free
        percent = (size - free)
        percent = percent / size * 100
        percent = Math.floor(percent) + '%'
        return percent;
    });
}
要访问get_disk_space函数作用域之外的结果,需要执行以下操作:

get_disk_space().then((result) => {
   //log and handle your result
   console.log(result);
   // handle your result
});
如果调用
get\u disk\u space
的函数是异步的,您只需执行以下操作:

async function testFunc() {
const result = await get_disk_space();
// handle result
}

因为它是异步的,所以return语句将转到下一个
then()
语句,这是您没有的。您可以调用包含处理结果的其余代码的函数,而不是返回结果。但仍然不能将结果带出范围之外。。我想将它另存为一个变量,而不是log它可能还签出了两个解决方案,仍然返回未定义:/lits just console.log(get_disk_space());