Question

我无法使用forEach获得所需的结果。假设以下代码产生了所需的结果：

function isEven(array) {
  var evenNum = [];
  for (var i = 0; i <= array.length; i++) {
    if (array[i] % 2 === 0)
      evenNum.push((array[i]));

  }
  return evenNum;
}

var output = isEven([1, 4, 5, 6, 10, 13]);
console.log(output); // --> [4, 6, 10]

// How do I get the same result with a forEach method?
//  My code reads:

function isEven(array) {
  var evenNum = [];
  array.forEach(function (currentValue) {
    if (currentValue % 2 === 0)
      evenNum.push(array[currentValue]);
  })
  return evenNum;
}

var output = isEven([1, 4, 5, 6, 10, 13]);
console.log(output); // --> [10, 10, 10] not desired

Answer 1

var numbers = [1,2,3,4,5,6,7,8,9,10];
var even;

For loop：

even = [];
for (var i = 0; i < numbers.length; ++i)
    if (numbers[i] % 2 === 0)
        even.push(numbers[i]);
console.log(even);

使用forEach：

even = [];
numbers.forEach(n => {
    if (n % 2 === 0)
        even.push(n);
});
console.log(even);

或者更简洁：

even = numbers.filter(n => (n % 2 === 0));
console.log(even);

Answer 2

当你应该直接使用currentValue时，看起来你正在索引数组。

function isEven(array){
    var evenNum = [];
    array.forEach(function(currentValue){
        if(currentValue % 2 === 0)
        evenNum.push(currentValue);
    })
    return evenNum;
}

Answer 3

你有evenNum.push(array[currentValue])。它应该是evenNum.push(currentValue)。

function isEven(array) {
  var evenNum = [];
  array.forEach(function (currentValue) {
    if (currentValue % 2 === 0)
      evenNum.push(currentValue);
  })
  return evenNum;
}

var output = isEven([1, 4, 5, 6, 10, 13]);
console.log(output); // --> [10, 10, 10] not desired

ForEach在一个函数JavaScript中

3 个答案: