为什么if语句不返回boolean和object类型的值？

Question

I'm curious as to why the else if statements in the filter method do not return anything:

var moveZeros = function (arr) {
  const nonZeros = arr.filter(value => {
    if (value !== 0) return value
    else if (typeof value === 'boolean') return value
    else if (typeof value === 'object') return value
  })

  const zeros = arr.toString().match(/0/g).map(Number)

  const newArr = nonZeros.concat(zeros) 

  return newArr
}

Additionally, I would also like to know why I get a similar effect when I try to filter out zeros from an array:

const zeros = arr.filter(value => {
  if (value === 0) return value
})

Here is a sample array to test the function:

[ 0, 1, null, 2, false, 1, 0 ]

Thank you for any help!

Answer 1

You don't need to return value in the filter method, return the boolean which should be true if the value should be selected, like so:

 var moveZeros = function (arr) { // also when you use !== 0, you don't need to check the type as it compares type const nonZeros = arr.filter(value => value !== 0) const zeros = arr.filter(value => value === 0) const newArr = nonZeros.concat(zeros) return newArr } console.log(moveZeros([ 0, 1, null, 2, false, 1, 0 ]));