如何使用javascript foreach循环获取返回四？

Question

There is an array and I want to use foreach loop to get the biggest number

Here is an array

 const array2 = ['a', 3, 4, 2]

What i try in JS:

 function biggestNumberInArray3(arr) {
  var largest = arr[0] || null;
  var number = null;
  arr.forEach (value => {
    number = value
    largest = Math.max(largest, number);
   })
  return largest;
  }

Looks like Math.max isn't work in here.

It returns NaN

Are there any other ways to use foreach loop to compare the elements in an array?

PS: this foreach loop will return 4

Answer 1

You should use Array.reduce to find the max number and filter it before the max operation as the presence of a will cause the result to be a NaN .

 const array2 = ['a', 3, 4, 2] var max = array2.filter((num)=> !isNaN(num)).reduce((a, b)=>{ return Math.max(a, b); }); console.log(max); 

Answer 2

forEach don't return any value.

You can use Filter and Math.max

1. use filter to remove all non-number values.
2. use Math.max to get highest value.

  const array2 = ['a', 3, 4, 2] console.log(Math.max(...array2.filter(e=> !isNaN(e)))) 

Answer 3

const array2 = ['a', 3, 4, 2]
var max = Math.max(...array2.filter(num => Number.isInteger(num)));
console.log(max);

Answer 4

Remove the string from array, see demo. Not interested in efficient and simple code? forEach() only returns undefined so you'll need to get a side-effect in order to get any result. In the demo below there's a variable outside the loop that changes as the loop progresses. Eventually this variable will be the greatest number in the array.

---

Demo

 /* Math.max.apply() ======================================*/ const array = ['a', 3, 4, 2]; //Get rid of the string const num = array.shift(); console.log(`Math.max.apply({}, arr) ========= ${Math.max.apply({}, array)}`); /* forEach() =======================================*/ let max = 0; array.forEach(num => { max = num > max ? max = num : max; }); console.log(`array.forEach() ================ ${max}`); 

Answer 5

If you want to use forEach , you can just add a check for numbers in your code

  function biggestNumberInArray3(arr) { var largest = null; var number = null; arr.forEach (value => { if(typeof(value) === "number"){ number = value largest = Math.max(largest, number); } }) return largest; } console.log(biggestNumberInArray3(['a', 3, 4, 2])) 

Answer 6

Here you have another solution using only reduce() :

 const array2 = ['a', 3, 4, 2, "hello", {hello:"world"}]; let res = array2.reduce((max, e) => isNaN(e) ? max : Math.max(max, e), null); console.log(res);