Question

我们说我有一个包含状态及其余额的对象。

    {
      "amount": "822370.71",
      "state": "ME"
    },
    {
      "amount": "968817.53",
      "state": "FL"
    },
    {
      "amount": "587603.26",
      "state": "OH"
    },
    {
      "amount": "657617.83",
      "state": "OH"
    },
    {
      "amount": "657617.83",
      "state": "FL"
    }

我如何添加属于每个州的金额，例如OH将具有587603.26 + 657617.83。我相信map（）方法将在这里使用，但我不知道如何使用它。谢谢！

Answer 1

使用Array.prototype.forEach()函数的简短解决方案：

＆＃13;

var arr = [{"amount": "822370.71","state": "ME"},{"amount": "968817.53","state": "FL"},{"amount": "587603.26","state": "OH"},{"amount": "657617.83","state": "OH"},{"amount": "657617.83","state": "FL"}],
    result = {};

arr.forEach(function (o) {
    var amount = Number(o.amount);
    (result[o.state])? result[o.state] += amount : result[o.state] = amount;
});

console.log(result);

＆＃13;

Answer 2

这是public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final EditText number1 = (EditText) findViewById(R.id.number1); final EditText number2 = (EditText) findViewById(R.id.number2); Button add = (Button) findViewById(R.id.btnAdd); Button sub = (Button) findViewById(R.id.btnSub); Button div = (Button) findViewById(R.id.btnDiv); Button mul = (Button) findViewById(R.id.btnMul); final TextView txtresult = (TextView) findViewById(R.id.result); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { double num1, num2, result; num1 = Double.parseDouble(number1.getText().toString()); num2 = Double.parseDouble(number2.getText().toString()); result = num1 + num2; txtresult.setText(Double.toString(result)); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { double num1, num2, result; num1 = Double.parseDouble(number1.getText().toString()); num2 = Double.parseDouble(number2.getText().toString()); result = num1 - num2; txtresult.setText(Double.toString(result)); } }); div.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { double num1, num2, result; num1 = Double.parseDouble(number1.getText().toString()); num2 = Double.parseDouble(number2.getText().toString()); result = num1 / num2; txtresult.setText(Double.toString(result)); } }); mul.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { double num1, num2, result; num1 = Double.parseDouble(number1.getText().toString()); num2 = Double.parseDouble(number2.getText().toString()); result = num1 * num2; txtresult.setText(Double.toString(result)); } }); } }，filter和map一起使用的完美用例。

reduce

Javascript：如何添加属于共享密钥的对象的值？

2 个答案: