Question

我已经列出了它所代表的船只清单：

var fleet = 
    ["RMS MARY", 2000, 15],
    ["TITANIC 2", 10000, 13],
    ["Boaty McBoatface", 2000, 18],
    ["Jutlandia", 1945, 10], 
    ["Hjejlen", 250, 8] 
];

我想编写一个按给定容量过滤船只的功能。例如：

filterByCapacity(fleet,5000)

这应该只返回Titanic 2号船只，因为它是唯一容量高于5000的船只。关于如何编写这样一个函数的任何想法？

Answer 1

简单：

System.TypeInitializationException: The type initializer for '<StartupCode$Company-EFeedbackExport>.$Repository' threw an exception. ---> System.ArgumentOutOfRangeException: No mapping exists from SqlDbType Date     to a known DbType.
Parameter name: SqlDbType
  at System.Data.SqlClient.SqlParameter.SetSqlDbType (SqlDbType type) <0x411a3080 + 0x00afb> in <filename unknown>:0
  at System.Data.SqlClient.SqlParameter.set_SqlDbType (SqlDbType value) <0x411a3040 + 0x00017> in <filename unknown>:0

  at (wrapper remoting-invoke-with-check) System.Data.SqlClient.SqlParameter:set_SqlDbType (System.Data.SqlDbType)
  at FSharp.Data.Sql.Providers.MSSqlServer.getDbType@27 (Int32 providerType) <0x411a17c0 + 0x0008b> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServer+mappings@38.GenerateNext (IEnumerable`1& next) <0x411999f0 + 0x007bb> in <filename unknown>:0
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1[T].MoveNextImpl () <0x41199790 + 0x00069> in <filename unknown>:0
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1[T].System-Collections-IEnumerator-MoveNext () <0x41199760 + 0x00017> in <filename unknown>:0
  at Microsoft.FSharp.Collections.SeqModule.ToList[T] (IEnumerable`1 source) <0x411991c0 + 0x001ea> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServer.createTypeMappings (IDbConnection con) <0x411761d0 + 0x00097> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServerProvider.FSharp-Data-Sql-Common-ISqlProvider-CreateTypeMappings (IDbConnection con) <0x411761a0 + 0x00013> in <filename unknown>:0
  at <StartupCode$FSharp-Data-SqlProvider>.$SqlRuntime.DataContext.f@1-29 (System.String runtimeAssembly, System.String resolutionPath, System.String[] referencedAssemblies, DatabaseProviderTypes providerType,     System.String owner, FSharp.Data.Sql.Runtime.SqlDataContext this, Microsoft.FSharp.Core.Unit unitVar0) <0x401883d0 + 0x00109> in <filename unknown>:0
  at FSharp.Data.Sql.Runtime.SqlDataContext..ctor (System.String typeName, System.String connectionString, DatabaseProviderTypes providerType, System.String resolutionPath, System.String[] referencedAssemblies,     System.String runtimeAssembly, System.String owner, CaseSensitivityChange caseSensitivity) <0x401880b0 + 0x00153> in <filename unknown>:0
  at <StartupCode$Company-EFeedbackExport>.$Repository..cctor () <0x40187650 + 0x002ab> in <filename unknown>:0
  --- End of inner exception stack trace ---
  at Program.main (System.String[] args) <0x4016de00 + 0x00087> in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.TypeInitializationException: The type initializer for '<StartupCode$Company-EFeedbackExport>.$Repository' threw an exception. ---> System.ArgumentOutOfRangeException: No     mapping exists from SqlDbType Date to a known DbType.
Parameter name: SqlDbType
  at System.Data.SqlClient.SqlParameter.SetSqlDbType (SqlDbType type) <0x411a3080 + 0x00afb> in <filename unknown>:0
  at System.Data.SqlClient.SqlParameter.set_SqlDbType (SqlDbType value) <0x411a3040 + 0x00017> in <filename unknown>:0

  at (wrapper remoting-invoke-with-check) System.Data.SqlClient.SqlParameter:set_SqlDbType (System.Data.SqlDbType)
  at FSharp.Data.Sql.Providers.MSSqlServer.getDbType@27 (Int32 providerType) <0x411a17c0 + 0x0008b> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServer+mappings@38.GenerateNext (IEnumerable`1& next) <0x411999f0 + 0x007bb> in <filename unknown>:0
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1[T].MoveNextImpl () <0x41199790 + 0x00069> in <filename unknown>:0
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1[T].System-Collections-IEnumerator-MoveNext () <0x41199760 + 0x00017> in <filename unknown>:0
  at Microsoft.FSharp.Collections.SeqModule.ToList[T] (IEnumerable`1 source) <0x411991c0 + 0x001ea> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServer.createTypeMappings (IDbConnection con) <0x411761d0 + 0x00097> in <filename unknown>:0
  at FSharp.Data.Sql.Providers.MSSqlServerProvider.FSharp-Data-Sql-Common-ISqlProvider-CreateTypeMappings (IDbConnection con) <0x411761a0 + 0x00013> in <filename unknown>:0
  at <StartupCode$FSharp-Data-SqlProvider>.$SqlRuntime.DataContext.f@1-29 (System.String runtimeAssembly, System.String resolutionPath, System.String[] referencedAssemblies, DatabaseProviderTypes providerType,     System.String owner, FSharp.Data.Sql.Runtime.SqlDataContext this, Microsoft.FSharp.Core.Unit unitVar0) <0x401883d0 + 0x00109> in <filename unknown>:0
  at FSharp.Data.Sql.Runtime.SqlDataContext..ctor (System.String typeName, System.String connectionString, DatabaseProviderTypes providerType, System.String resolutionPath, System.String[] referencedAssemblies,     System.String runtimeAssembly, System.String owner, CaseSensitivityChange caseSensitivity) <0x401880b0 + 0x00153> in <filename unknown>:0
  at <StartupCode$Company-EFeedbackExport>.$Repository..cctor () <0x40187650 + 0x002ab> in <filename unknown>:0
  --- End of inner exception stack trace ---
  at Program.main (System.String[] args) <0x4016de00 + 0x00087> in <filename unknown>:0

但我建议您使用对象而不是数组。更像是这样：

function filterByCapacity(fleet, capacity) {
    var filteredArray = [];
    for (var i = 0; i < fleet.length; i++) {
        // Supposing we know that the capacity is the second index in the array
        if (fleet[i][1] >= capacity)    // Or you can make this strictly greather than (>)
            filteredArray.push(fleet[i]);
    }
    return (filteredArray);
}

这样你可以制作一个通用函数var fleet = [ { name: "RMS MARY", capacity: 2000, age: 15, // I had no idea what the third index meant so I made up one }, { name: "TITANIC 2", capacity: 10000, age: 13, }, { name: "Boaty McBoatface", capacity: 2000, age: 18, }, { name: "Jutlandia", capacity: 1945, age: 10, }, { name: "Hjejlen", capacity: 250, age: 8, } ];，它可以返回与过滤器相匹配的船只

Answer 2

首先，我想指出你的阵列制作得很糟糕。您在第一个条目（“RMS MARY”）上缺少左方括号。更正后的数组如下：

var fleet = [
    ["RMS MARY", 2000, 15],
    ["TITANIC 2", 10000, 13],
    ["Boaty McBoatface", 2000, 18],
    ["Jutlandia", 1945, 10], 
    ["Hjejlen", 250, 8], 
];

其次，我建议您使用对象代替数组，而不是数组，所以你有这样的东西：

var fleet = {
    {name: "RMS MARY", capacity: 2000, somethingElse: 15},
    {name: "TITANIC 2", capacity: 10000, somethingElse: 13},
    {name: "Boaty McBoatface", capacity: 2000, somethingElse: 18},
    {name: "Jutlandia", capacity: 1945, somethingElse: 10},
    {name: "Hjejlen", capacity: 250, somethingElse: 8},
};

现在，对于你想要的函数，我将提供两个，一个用于船只的原始数组表示，一个用于对象表示：

//array representation
function filterByCapacity(fleet, capacity){
    return fleet.filter(function(ship){
        return ship[1] >= capacity;
    });
}

//object representation
function filterByCapacity(fleet, capacity){
    return fleet.filter(function(ship){
        return ship.capacity >= capacity;
    });
}

希望这有帮助。

Answer 3

将您的船舶表示为物体：

var fleet = [
  {name: "RMS Mary", capacity: 2000, whatever: 15},
   ...
];

然后，您可以以可读且有意义的方式使用过滤器。

function filterByCapacity(fleetArr, minCapacity) {
  return fleetArr.filter(function(ship) {
    return ship.capacity > minCapacity;
  });
}
console.log(filterByCapacity(fleet, 5000)) // only Titanic

JavaScript过滤器数组功能

3 个答案: