What is the best way to retrieve data from within a for loop in javascript?

Question

What is the best way to retrieve data from within a for loop in javascript?

Seeking assistance in Typescript (javascript) to ensure that the code inside the for loop completes execution before returning

I have a text box where users input strings, and I'm searching for numbers following '#'. I've created a function to find the starting index of '#' and now need to extract only the numbers after '#'. Currently, I am using a for loop to iterate through the string to identify the number value. However, it seems that the return statement is executed prior to the completion of the for loop. How can I adjust this so that the return waits for the for loop to finish and update the internal variable before proceeding?...

  readNumber(text: string): number {
    const start = text.indexOf('#') + 1;
    let newText = '';
    for (let index = start; index < text.length; index++) {
      if (text.slice(index, 1) === ' ') {
        newText = text.slice(start, index - start);
      }
    }
    return +newText;
  }

If the user enters "employee #56 cv," I expect the output to be 56.

javascript typescript promise

Answer 1

Answer №1

After assigning to newText, the loop will indeed continue. To halt it at that point, you can include a break:

newText = text.slice(start, index - start);
break;

Alternatively, you can bypass the loop entirely by utilizing indexOf once more:

readNumber(text: string): number {
  const start = text.indexOf('#') + 1;
  if (start === -1) {
      return 0; // You can specify another value to return when '#' is not found
  }
  let end = text.indexOf(' ', start);
  if (end === -1) {
      end = text.length;
  }
  return +text.substring(start, end);
}

You may also opt for a regular expression method:

readNumber(text: string): number {
  const match = /[^#]*#(\d+)/.exec(text);
  if (!match) {
      return 0; // You can define a different return value if '#' is absent
  }
  return +match[1];
}

This approach is slightly altered from your example as it captures a sequence of digits instead of looking for a space. If you prefer to use a space instead:

readNumber(text: string): number {
  const match = /[^#]*#([^ ]*)(?: |$)/.exec(text);
  if (!match) {
      return 0; // You can specify an alternative return value in case '#' is missing
  }
  return +match[1];
}

Answer 2

After assigning to newText, the loop will indeed continue. To halt it at that point, you can include a break:

newText = text.slice(start, index - start);
break;

Alternatively, you can bypass the loop entirely by utilizing indexOf once more:

readNumber(text: string): number {
  const start = text.indexOf('#') + 1;
  if (start === -1) {
      return 0; // You can specify another value to return when '#' is not found
  }
  let end = text.indexOf(' ', start);
  if (end === -1) {
      end = text.length;
  }
  return +text.substring(start, end);
}

You may also opt for a regular expression method:

readNumber(text: string): number {
  const match = /[^#]*#(\d+)/.exec(text);
  if (!match) {
      return 0; // You can define a different return value if '#' is absent
  }
  return +match[1];
}

This approach is slightly altered from your example as it captures a sequence of digits instead of looking for a space. If you prefer to use a space instead:

readNumber(text: string): number {
  const match = /[^#]*#([^ ]*)(?: |$)/.exec(text);
  if (!match) {
      return 0; // You can specify an alternative return value in case '#' is missing
  }
  return +match[1];
}

What is the best way to retrieve data from within a for loop in javascript?

Answer №1

Similar questions

Using Jquery to dynamically add an active class to a link if it matches the current URL

How can you temporarily stop an event with a click or touch, and then resume the event's state after performing certain tasks in jQuery?

A guide on sending a post request with Axios to a parameterized route in Express

The character 'T' cannot be assigned to the data type 'number'

A comprehensive guide on personalizing Bootstrap 4 tooltips to suit your specific needs

Is there a way to update the button's value upon clicking it?

I'm looking to add autocomplete functionality to a text input in my project, and then retrieve and display data from a MySQL database using

Choose a phrase that commences with the term "javascript"

ES6 promises: the art of connecting functions with parameters

When I navigate to the About page in Vue, the data is automatically cleared

What is the best way to include a select HTML element as an argument in an onSubmit form function call?

Vue.js is displaying one less item

Is it possible to execute MongoDB queries from an AS3 client?

JavaScript OOP Function call not functioning in IE9

Error: Uncaught promise rejection - The function is undefined in the context of Vue.js and Electron

The next function is not defined error in the controller function

Retrieving input values with JQuery

Activate the HTML drop-down option upon selecting the radio button, or the other way around

The dangers posed by vulnerabilities in the React library

Node.js server containerized with Docker: deleted express route remains accessible