JS算法题之查找数字在数组中的索引位置

function getIndexToIns(arr, num) {
 return num;
}

getIndexToIns([40, 60], 50);

let food = ['pizza', 'ice cream', 'chips', 'hot dog', 'cake']
food.indexOf('chips')
// returns 2
food.indexOf('spaghetti')
// returns -1

let array = [4, 10, 20, 37, 45]
array.push(98)
// returns 6
array.concat(98)
// returns [4, 10, 20, 37, 45, 98]

function getIndexToIns(arr, num) {
 // Insert num into arr, creating a new array.
  let newArray = arr.concat(num)
 //    [40, 60].concat(50)
 //    [40, 60, 50]

 // Sort the new array from least to greatest.
  newArray.sort((a, b) => a - b)
 // [40, 60, 50].sort((a, b) => a - b)
 // [40, 50, 60]

 // Return the index of num which is now
 // in the correct place in the new array.
  return newArray.indexOf(num);
 // return [40, 50, 60].indexOf(50)
 // 1
}

getIndexToIns([40, 60], 50);

function getIndexToIns(arr, num) {
 return arr.concat(num).sort((a, b) => a - b).indexOf(num);
}

getIndexToIns([40, 60], 50);

let numbers = [3, 17, 94, 15, 20]
numbers.findIndex((currentNum) => currentNum % 2 == 0)
// returns 2
numbers.findIndex((currentNum) => currentNum > 100)
// returns -1

function getIndexToIns(arr, num) {
 // Sort arr from least to greatest.
 let sortedArray = arr.sort((a, b) => a - b)
 //     [40, 60].sort((a, b) => a - b)
 //     [40, 60]

 // Compare num to each number in sortedArray
 // and find the index where num is less than or equal to 
 // a number in sortedArray.
 let index = sortedArray.findIndex((currentNum) => num <= currentNum)
 //   [40, 60].findIndex(40 => 50 <= 40) --> falsy
 //   [40, 60].findIndex(60 => 50 <= 60) --> truthy
 //   returns 1 because num would fit like so [40, 50, 60]

 // Return the correct index of num.
 // If num belongs at the end of sortedArray or if arr is empty 
 // return the length of arr.
 return index === -1 ? arr.length : index
}

getIndexToIns([40, 60], 50);

function getIndexToIns(arr, num) {
 let index = arr.sort((a, b) => a - b).findIndex((currentNum) => num <= currentNum)
 return index === -1 ? arr.length : index
}

getIndexToIns([40, 60], 50);