如何在不使用 method.length 的情况下计算数组中元素的数量

Question

function addValue(arr, value){

arr.push(value)

return...

}

console.log(addValue([1, 2, 3], 10)); // 4 without using.length

Answer 1

Array#push returns the new length of the array.

 function addValue(arr, value) { return arr.push(value); } console.log(addValue([1, 2, 3], 10)); // 4 without using.length

Answer 2

Try this pure javascript return length of the array without.length

var a = [1,2,3,4,5];

function arrayLength(a){
  var length = 0;
  while(a[length]!==undefined){
    length++;
  }
  return length;
}

console.log(arrayLength(a));       // 5

Answer 3

function addValue(arr, value){

arr.push(value)
var count=0;
arr.forEach(a=>{
count++;})
return count

}

console.log(addValue([1, 2, 3], 10)); 

Answer 4

If you don't want to use.length, then you can make your own length variable by manually counting them

function addValue(arr, value){

    arr.push(value)

    return ( ()=> {
         var mylength=0
         for(var k in a) mylength+=1
         return mylength
    } )()

}

Although I'm guessing the reason you don't want to use.length is simply because your using some kind of sudo-array that doesn't have a length property, in which case you can just convert it to an array

....
return Array.apply(null, ar).length

If not though length is pretty much what you want

Another option, again, as shorthand for counting the elements, is to just the length of a list of the keys

return Object.keys(ar).length

Or Object.values

return Object.values(ar).length

Or Object.entries

return Object.entries(ar).length

(Usually these methods are good for sudo-array or custom arrays made from scratch that don't have a length property)

Or just return the push function

return ar.push(value)