While loop needs extra condition

JavaScript
1

inside the while loop if i don’t include the if(j>0) , it breaks on the first cycle, saying ‘cannot set properties of undefined’. But the while loop doesn’t initiate when j is below 1 anyway. which i can check with the console.log. So don’t understand why it won’t just perform the ‘swap’.

  **Your code so far**


function insertionSort(arr) {
let result=[]
for(let i=0;i<arr.length;i++){
  result.push(arr[i])
  let element=result[i]
  let j=i
  while (element<result[j-1]) {
    console.log('j=',j,' j-1=',j-1)
    if(j>0)[ result[j-1], result[j] ] = [ result[j], result[j-1] ]
    j--
  }
}
return result;
}
console.log(insertionSort([5,4,2,8,345,123,43,32,5643,63,123,43,2,55,1,234,92]))

  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.5005.61 Safari/537.36

Challenge: Implement Insertion Sort

Link to the challenge:

2

[quote=“ugwen, post:1, topic:511861”]

let result=[]
for(let i=0;i<arr.length;i++){
  result.push(arr[i])
  let element=result[i]
  let j=i
  while (element<result[j-1]) {
    console.log('j=',j,' j-1=',j-1)
    if(j>0)[ result[j-1], result[j] ] = [ result[j], result[j-1] ]
    j--
  }
}
return result

hello and welcome to fcc forum :slight_smile:
can you not use “map / sort” array method in that “insertionSort()”

3

not sort at least. we are to avoid provided funtions. i already figured out a better way, it’s just this point botherss me.

4

as in compare and replace?

5

yes, thats wat it is. i just happen to create a new array here. i know how to correct that tho.

6

What is 0-1?

7

that’s got me really confused.

  • firstly trying to figure out where i had ‘0-1’.
  • then i realized element<result[j-1] equates to true when result[j-1]=undefined (unintended).

then i realised it works fine without the logs:

while (element<result[j-1]) {
    // console.log('j=',j,' j-1=',j-1)
    [ result[j-1], result[j] ] = [ result[j], result[j-1] ]
    j--
  }

weird

8

console.log should not cause any problem in code!! unless it breaks it’s enclosing element syntax

2 Likes
9

You still need to account for your bounds on j somehow. result[-1] isn’t defined.

10

yes, i can see good practice would be to avoid result[-1] ahead of the while loop. still a weird behaviour with the logs affecting it, but i’ll put it down to that oversight and move on. thanks.

11

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