I asked a similar question here TypeScript: How to replace a particular number in a string, and then update its value?

Really appreciate the answers there. It answered my questions.

I am run into a new issue. Thought it s more helpful to raise a new question while referring to the old question.

I have a column that is full of 10-digits string.

Sometimes that entire 10-digits only contain numerical values (e.g. 3345678901), but sometimes there is dash included (e.g. 3345678---)

I would like to be able to:

1. Input an index number X
2. Locate the corresponding number in the string
3. Add or subtract a particular number A to/from that number to update the string
4. Update the string

Example 1 (all numerical): 3345678901

• Input index number "4"
• The corresponding number is 6
• Increase that number by 2 to 8
• Update the string to 3345878901

Example 2 (numerical & non-numerical): 3345678---

• Input index number "4"
• The corresponding number is 6
• Increase that number by 2 to 8
• Update the string to 3345878---

Example 3 (numerical & non-numerical): 3345678---

• Input index number "7"
• The corresponding value is -
• Increase (or rather, update) that number by 2 to 2
• Update the string to 33458782--

For example 1, I know I could do following (as a contributor from the OG post has pointed out):

const givenStr = "3345678901";

let givenStrArray = givenStr.split('').map(Number);

const inputIndex = 4;
const increaseAmount = 2;

givenStrNumber  = increaseAmount

console.log(givenStrNumber);

But, how do I go about Example 2 and 3 though? Since there are string '-' involved? In this case map(Number) would lead to Null values that would break the code.

Any help would be greatly appreciated!

CodePudding user response：

Check for NaN. This is a tiny snippet that would give you a hint:

// ...
// ...
const increment = 2;

let givenStrArray = 
  givenStr
   .split('')
   .map((digiit) => isNaN(digit) ? increment : Number(digit   increment);

// ...
// ...

CodePudding user response：

This should do the trick

let str = '3345678---'

let NumericStrArray = str.split('').map(x => Number.isNaN(Number(x)) ? x: Number(x))

let ipIndex = 7
let incAmount = 2
let val = NumericStrArray[ipIndex]
NumericStrArray[ipIndex] = typeof val === 'string' ? incAmount : val   incAmount

let result = NumericStrArray.join('')

ps: It is not a good practice to use global isNaN as shown in the different answers above / below

We should use Number.isNaN() in all cases if possible.

MDN DOCS WITH EXPLANATION

CodePudding user response：

Here's a simple little snippet. Break the sting apart, map through each item, when we find the index we need to update we update it and return it, then join them all back together.

Multiple conditional ternary operator have been used here, you can find out more about how they work here: Conditional (ternary) operator

const givenStr = "334567----", 
  inputIndex = 6,
  increaseAmount = 2

let givenNumber = givenStr
  .split('')
  .map((v,i) => i === inputIndex ? isNaN(v) ? increaseAmount :  v   increaseAmount : v)
  .join('')

console.log(givenNumber);