返回包含條件的數組的長度

Question

function(people){

}
people([{name: 'John', age: 22},{name: 'paul', age: 23},{name: 'mathew', age: 24},])

如何返回由年齡超過 22 歲的人組成的數組的長度，該數組的長度應為 2。

Answer 1

您可以使用數組減少來計數：

 function people(array){ return array.reduce((total, current)=>{ if(current.age>22) total = total +1; return total; },0); } console.log(people([{name: 'John', age: 22},{name: 'paul', age: 23},{name: 'mathew', age: 24},]));

Answer 2

以下是針對您的問題的函數式編程方法：

 const persons = [ {name: 'John', age: 22}, {name: 'paul', age: 23}, {name: 'mathew', age: 24} ] const over22 = persons.filter(person => person.age > 22) console.log('there are', over22.length, 'people aged over 22')

希望這可以幫助。 干杯，

Answer 3

請嘗試以下操作：

function find_length(checkField, valueField, myArray) {
  for (var i = 0; i < myArray.length; i++) {
      if (myArray[i][checkField] == valueField) {
         return Object.keys(myArray[i]).length;
      }
  }
}

var myList = [{name: 'John', age: 22}, {name: 'paul', age: 23}, {name: 'mathew', age: 24},];
var ageObjLength = find_length('age', '22', myList );
alert("Length is " + ageObjLength);