JSON数组Angular 6的比较

Question

我有两个不同的JSON对象：

a = [{id:"1",time:"timestamp"},{id:"2",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"},{id:"5",time:"timestamp"}];
b = [{id:"1",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"}];

我想根据数组a中的匹配创建一个新数组。例如，上面示例中的输出如下所示：

c = ["1","0","1","1","0"]

其中1表示我们找到id的情况，0表示我们没有得到id的情况。

到目前为止，我尝试了以下方法：

c = [];

var val = JSON.parse(b);
if (val.length > 0) {
  val.forEach((obj) => {
    var match = a.find(({
      id
    }) => obj.id === id);
    if (!match) {
      c.push("0");
    } else {
      c.push("1");
    }
  });
}
console.log(c);

有人能告诉我我做错了什么吗？

谢谢

Answer 1

据我所知，你应该反过来做。如果要检查第一个列表的值是否在第二个列表中，则需要循环第一个列表，而不是第二个列表。

c = [];

    var val = JSON.parse(a);
    if( val.length > 0 ) {
       val.forEach((obj)=>{
         var match = b.find(({id}) => obj.id === id);
         if(!match){
           c.push("0");
         }
         else {
           c.push("1");
         }
       });
    }
    console.log(c);

Answer 2

你需要在a中使用forEach，然后在b中找到一个元素。

​

var a = [{id:"1",time:"timestamp"},{id:"2",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"},{id:"5",time:"timestamp"}];
var b = [{id:"1",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"}];

var c = [];
var val = a;

if (val.length > 0) {
  val.forEach((obj) => {
    var match = b.find(({
      id
    }) => obj.id === id);
    if (!match) {
      c.push("0");
    } else {
      c.push("1");
    }
  });
}
console.log(c);

​

Answer 3

使用简单的For循环；

​

 a = [{id:"1",time:"timestamp"},{id:"2",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"},{id:"5",time:"timestamp"}];
    b = [{id:"1",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"}];

    var arr  = [];
    var a_keys =  a.map(e => e.id);
    var b_keys =  b.map(e => e.id);
    
    for(var i=0;i<a_keys.length;i++){
        if(b_keys.indexOf(a_keys[i]) != -1){
           arr.push('1');
       }else{
       arr.push('0');
       }
    }

    console.log(arr);

​

​

a = [{id:"1",time:"timestamp"},{id:"2",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"},{id:"5",time:"timestamp"}];
    b = [{id:"1",time:"timestamp"},{id:"3",time:"timestamp"},{id:"4",time:"timestamp"}];

    var arr  = [];

    
    for(var i= 0; i < a.length; i++) {
        for(var j= 0; j < b.length; j++) {
         if(a[i].id ===  b[j].id){
          arr.push('1');
          break;
         }
         if((a[i].id !==  b[j].id) && (j === (b.length - 1))){
             arr.push('0');
         }
       }
     }

    console.log(arr);

​