判斷數組對象中是否有某個屬性值

 var user = [
 {
      id: 1,
      name: "李四"
  },
  {
      id: 2,
      name: "張三"
  },
  {
      id: 3,
      name: "李五"
  }
]

判斷以上數組是否含有 name爲“李五”的數據

 // 如果有就返回
 function findElem(arrayToSearch, attr, val) {
   for (var i = 0; i < arrayToSearch.length; i++) {
        if (arrayToSearch[i][attr] == val) {
            return i;
        }
    }
    return -1;
}
console.log(findElem(user,'name',"李四")); // 0
console.log(findElem(user,'id',7)); // -1
console.log(findElem(user,'id',3)); // 2