firebase数据库推送方法使用唯一键向数据库子项添加对象,例如, postsRef.push({ author: "gracehop", title: "Announcing COBOL, a New Programming Language"}); 在数据库中放置如下内容 "posts": { "-JRHTHaIs-jNPLXOQi
          postsRef.push({
  author: "gracehop",
  title: "Announcing COBOL, a New Programming Language"
}); 
 在数据库中放置如下内容
"posts": {
    "-JRHTHaIs-jNPLXOQivY": {
      "author": "gracehop",
      "title": "Announcing COBOL, a New Programming Language"
    } 
 但是,如果我将push方法与对象数组一起使用,例如
postsRef.push({
        {
          author: "gracehop1",
          title: "Announcing COBOL, a New Programming Language"
        },
        {
          author: "gracehop2",
          title: "Announcing COBOL, a New Programming Language"
        }}); 
 我在数据库中获得了一个具有枚举对象的唯一键,即
"posts": {
    "-JRHTHaIs-jNPLXOQivY": {
      "0": { 
         "author": "gracehop1",
         "title": "Announcing COBOL, a New Programming Language"
       },
      "1": {
         "author": "gracehop2",
         "title": "Announcing COBOL, a New Programming Language"
       }
     }} 
 有没有办法在单个事务中推送一个对象数组,这样我就可以获得数组中每个对象的唯一键,即结果看起来像
"posts": {
        "-JRHTHaIs-jNPLXOQivY": {
             "author": "gracehop1",
             "title": "Announcing COBOL, a New Programming Language"
         "-JRHTHaIs-jNPLXOQivZ": {
             "author": "gracehop2",
             "title": "Announcing COBOL, a New Programming Language"
           }
         }}
 一个鲜为人知的事实是你可以在没有任何参数的情况下调用push(),它只会为你生成一个位置/推送ID.通过该位置和多位置更新(请参阅 
 here和 
 here),您可以执行以下操作: 
  
  
 var key1 = postsRef.push().key;
var key2 = postsRef.push().key;
var updates = {};
updates[key1] = {
      author: "gracehop1",
      title: "Announcing COBOL, a New Programming Language"
    };
updates[key2] = {
      author: "gracehop2",
      title: "Announcing COBOL, a New Programming Language"
    };
ref.update(updates);
        
             