How find the array index for two array comparision and return once array item less than another?-CodePudding

I would like to compare two array then return the index once first array less than second array. But if the start value of first array greater than the second array, must skip until first array value less than second array. For example

case1: This must return index = 2 (exampleArr1 < exampleArr2 at index =2)

   var exampleArr1 = [15,9,7,5,3,1];
   var exampleArr2 = [2,6,8,12,17,22];

  function compareArray(exampleArr1,exampleArr2){
    ...
    return result
  }

case2: This must return index = 6 (exampleArr1 < exampleArr2 at index =6)

   var exampleArr1 = [1,2,4,5,15,9,7,5,3];
   var exampleArr2 = [2,3,5,6,2,6,8,12,17];

  function compareArray(exampleArr1,exampleArr2){
    ...
    return result
  }

Any advice or guidance on this would be greatly appreciated, Thanks.

CodePudding user response：

A simple for loop will suffice. In our loop, we already have the index so we just compare the first array at this index with the second array at this index.

const compareArray = (arr1, arr2) => {  
  let startIndex = 0
  if (arr1[0] < arr2[0]) {
    // find the index from arr1 that is greater than arr2
    startIndex = arr1.findIndex((a, index) => a > arr2[index])
  }

  for (let i = startIndex; i < arr1.length; i  ) {
    if (arr1[i] < arr2[i]) {
      return i
    }
  }
}

const exampleArr1 = [15,9,7,5,3,1]
const exampleArr2 = [2,6,8,12,17,22]
const exampleArr3 = [1,2,4,5,15,9,7,5,3]
const exampleArr4 = [2,3,5,6,2,6,8,12,17]

console.log(compareArray(exampleArr1, exampleArr2))
console.log(compareArray(exampleArr3, exampleArr4))

CodePudding user response：

Please use the findIndex method in your function like

var exampleArr1 = [15,9,7,5,3,1];
var exampleArr2 = [2,6,8,12,17,22];

function compareArray(exampleArr1,exampleArr2) {
    if (exampleArr1[0] < exampleArr2[0]) {
        exampleArr1 = exampleArr1.slice(1);
    }
    return exampleArr1.findIndex(function(e, i) { return exampleArr2[i] > e; });
}

console.log(compareArray(exampleArr1, exampleArr2));