Sorting through a list of strings by checking for a specific character within each string

Question

Sorting through a list of strings by checking for a specific character within each string

After spending years dabbling in VBA, I am now delving into Typescript.

I currently have an array of binary strings

Each string represents a binary number

My goal is to filter the array and extract all strings that contain '1' at position X

I have successfully written a traditional function to accomplish this task

    function CountOnes( ipArray: string[], ipIndex: number): number
    {
        var myCount:number=0
        for (var ipString of ipArray)
        {
            if (ipString[ipIndex]==="1") { myCount+=1}
        }
        return myCount
    }

However, I am struggling to achieve the same result using the .filter method. (where myData is the array of strings and myIndex is the position)

    myCount = myData.filter((x:string, myIndex:number) => x[myIndex]==="1").length)

I'm unsure about what I am missing. Can someone suggest a solution using the .reduce method?

It's important to note that I have been able to use the filter method in both VBA and Nim to achieve similar goals (VBA required me to create a FilterIt class), so I am puzzled as to why I am facing difficulties in Typescript/Javascript.

javascript typescript

Answer 1

Answer №1

You're so close to the solution, just a couple of adjustments are needed. Remember, in the closure you pass to the filter function, the second argument is actually the index of the element x, not the one you want to check against. Also, there seems to be an extra closing bracket in your code snippet.

To fix these issues, try this revised code:

const myIndex = 3;
const myCount = myData.filter((x: string) => x[myIndex] === "1").length;

Notice how the closure captures the variable myIndex from the surrounding scope.

Alternatively, you can use the reduce method like this:

const myIndex = 3;
const myCount = myData.reduce((count: number, x: string) => count += (x[myIndex] === "1") ? 1 : 0, 0);

Answer 2

You're so close to the solution, just a couple of adjustments are needed. Remember, in the closure you pass to the filter function, the second argument is actually the index of the element x, not the one you want to check against. Also, there seems to be an extra closing bracket in your code snippet.

To fix these issues, try this revised code:

const myIndex = 3;
const myCount = myData.filter((x: string) => x[myIndex] === "1").length;

Notice how the closure captures the variable myIndex from the surrounding scope.

Alternatively, you can use the reduce method like this:

const myIndex = 3;
const myCount = myData.reduce((count: number, x: string) => count += (x[myIndex] === "1") ? 1 : 0, 0);

Answer 3

Answer №2

Take a look at this revised version:

 function CountOnes( ipArr: string[], idx: number): number
    {
        var count:number=0
        for (var str of ipArr)
        {
            if (str[idx]==="1") { count+=1}
        }
        return count
    }

For the given array:

["01000", "00111", "110000"]

In the initial implementation, the variable idx is the index you provide. However, in the filter section

 count = myData.filter((x:string, innerIdx:number) => x[innerIdx]==="1").length)

The innerIdx here represents the position of the element x in the array myData. This could lead to inaccuracies in the result. Consider the following fix:

function CountOnes( ipArr: string[], idx: number): number
    {
        return ipArr.filter((x:string) => x[idx]==="1").length)
    }

Answer 4

Take a look at this revised version:

 function CountOnes( ipArr: string[], idx: number): number
    {
        var count:number=0
        for (var str of ipArr)
        {
            if (str[idx]==="1") { count+=1}
        }
        return count
    }

For the given array:

["01000", "00111", "110000"]

In the initial implementation, the variable idx is the index you provide. However, in the filter section

 count = myData.filter((x:string, innerIdx:number) => x[innerIdx]==="1").length)

The innerIdx here represents the position of the element x in the array myData. This could lead to inaccuracies in the result. Consider the following fix:

function CountOnes( ipArr: string[], idx: number): number
    {
        return ipArr.filter((x:string) => x[idx]==="1").length)
    }

Sorting through a list of strings by checking for a specific character within each string

Answer №1

Answer №2

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