javascript从回调返回(计时)为变量赋值 [英] javascript assigning value to variable from callback return (timing)

问题描述

我在将 Firebase 调用函数的返回值分配给我的全局变量时遇到了问题.这是我的功能:

I'm having a trouble with assigning return value from Firebase call function to my global variable. This is my function:

  function getThePushNameById( path , id ){
    path.once( 'value', function( data ){ 
        if( data.child('id').val() != id ){
            data.forEach( function( newData ){
                var base = new Firebase( path.child( newData.name() ).toString() );
                getThePushNameById( base, id );
            })
        }else{
            //finishes the function when path is founded - returns the value
            return path.name();
        }       
    })
}

这是我设置请求的另一个文件:

and this is the other file where I set the request:

var base = new Firebase(path/to/my/base);

var output = getThePushNameById( base , 2 )
console.log(output);

所以我的问题是 console.log 不等待 output 被定义，而是自己运行并记录 undefined.我的问题是，如果有人知道如何让 console.log 等待值?

So my problem is that console.log doesn't wait for output to be defined, but runs itself and logs undefined. And my question is if someone knows how can I make console.log wait for value?

推荐答案

function getThePushNameById( path , id, callback ){
    path.once( 'value', function( data ){ 
        if( data.child('id').val() != id ){
            data.forEach( function( newData ){
                var base = new Firebase( path.child( newData.name() ).toString() );
                getThePushNameById( base, id , callback ); //here was the error
            })
        }else{
            //finishes the function when path is founded - returns the value
            callback(path.name());
        }       
    })
}

getThePushNameById( base, 2, function(output) {
    console.log(output);
});

发现一个错误:当函数再次调用自身时，回调没有返回定义，所以它返回了一个未定义的.这段代码现在可以正常运行了

founded an error: callback was not back defined when function called itself again, so it returned an undefined. this code is now ok and works well

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