How can I do this?

Question

I know javascript has a replace method for strings and regular expressions, but I need to replace a number in an array with another array. Is this possible? If so, I am open to suggestions.

Answer 1 · 2018-05-07T23:13:09Z

May 7, 2018 11:13pm

This seems to work.

let unchangedArray = [0, 1, 2]

function replaceNumberInArray(currentArray, indexOfNumberToReplaceInCurrentArray, replacementArray) {
  let result = currentArray.map(function(element, index) {
    if (index == indexOfNumberToReplaceInCurrentArray) {
      return element = replacementArray;
    } else {
        return element;
    }
  });

  return result;
}

replaceNumberInArray(unchangedArray, 0, [10, 20, 30]); // returns  [ [10, 20, 30], 1, 2 ]

Our replaceNumberInArray() function iterates over a supplied array, and once it finds the index you specified, it replaces that index value with whatever replacement array you specified. It then returns the new array.

Map is a method you can call off of arrays. It iterates over all the values in the array, performs some kind of logic (that generally includes some kind of transformation of the current iteration's value), and then returns a new array. The block of the function() passed as an argument of map() is where logic is specified that will be executed for each value iteration. the arguments of that function(element, index) give you access to a reference of the element being iterated over (in this case, the element) and the index of that element in the array (in this case, index).

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

Answer 2 · 2018-05-09T23:53:53Z

May 9, 2018 11:53pm

Thanks so much Joseph you're a lifesaver. Will definitely be using moment.js library in the future for dates. Do you know of any courses that go into depth on this library? I'd love to learn more about it

Answer 3 · 2018-05-08T00:28:50Z

May 8, 2018 12:28am

Thank you Joseph, I will try that but first I want to make sure we're more clear on what I'm talking about, because I was pretty vague about the question. I am trying to sort dates. Each date is in an array, all inside another array. I want to sort them by year first, then replace the sorted year with its corresponding date. Voila. Dates sorted. My problem is I need to replace each year with its date in the sorted array, and I'm not exactly sure how

Answer 4 · 2018-05-08T00:31:10Z

May 8, 2018 12:31am

In other words, I need to get the original date array each year came from, and replace the year with it

Answer 5 · 2018-05-08T02:23:32Z

May 8, 2018 2:23am

Sure, give me a minute

Answer 6 · 2018-05-08T02:35:18Z

May 8, 2018 2:35am

<html>
<head></head>
<body>
  <h1>Sorting Dates</h1>
  <h3>Input dates in MM/DD/YYYY and they will be sorted in chronological order. Click Enter to enter each date and Sort when you want to sort your dates</h3>
  <input type = text> <button>Enter</button> <button>Sort</button>
  <script src = cryena.js></script>
  </body>
</html>

window.onload = function() {

let input = document.getElementsByTagName('input')[0];
let buttons = document.getElementsByTagName('button');

let storagearr = [];
let datearr = [];
let date;
let split;
let years = [];
let months = [];
let days = [];
let sortedYears;
let sortedMonths;
let sortedDays;

  buttons[0].addEventListener('click', () => {

   date = input.value;
   split = date.split('/');

   if (!split[1]) {
    alert('Please enter a valid date in the following format: MM/DD/YYYY | Example: 05/19/2018');
   }

  else if (isNaN(split[0]) || isNaN(split[1]) || isNaN(split[2])) {
   alert('You must input numbers as your dates');
  }

  else if (split[0] < 1 || split[0] > 12 || split[1] < 1 || split[1] > 31) {
   alert('Your month or day is invalid. (Program accepts days up to 31, even for months that do not have 31 days)');
  }

  else if (split[2].length !== 4) {
   alert('Year format must be YYYY');
  }

  else {

    for (let a = 0; a < split.length; a ++) {
    split[a] = parseInt(split[a]);
  }

    datearr.push(split);
  }

});

  buttons[1].addEventListener('click', () => {

   if (!datearr[0]) {
    alert('You must input at least one date');
  }

else {

   for (let b = 0; b < datearr.length; b ++) {

    months.push(datearr[b][0]);
    days.push(datearr[b][1]);
    years.push(datearr[b][2]);
  }

  sortedYears = years.sort(function() {
    return a - b;
  }); // want to replace sorted years with their corresponding dates

  for (let c = 0; c < sortedYears.length; c ++) {
    if (sortedYears[c - 1] == sortedYears[c] || sortedYears[c + 1] == sortedYears[c]) {
      secondLevel();
    }
  }

  function secondLevel() {

    sortedMonths = months.sort(function() {
      return a - b;
    }); // want to replace the sorted months with their corresponding years

    for (let d = 0; d < sortedMonths.length; d ++) {
      if (sortedMonths[d - 1] == sortedMonths[d] || sortedMonths[d + 1] == sortedMonths[d]) {
        thirdLevel();
      }
    }
  }

  function thirdLevel() {
    sortedDays = days.sort(function() {
      return a - b;
    }); // want to replace the sorted days with their corresponding months
  }
}
});
};

Answer 7 · 2018-05-08T14:57:19Z

May 8, 2018 2:57pm

Hmm...

I'm not sure I would go that route to sort dates. If you're not constrained to that approach, I'd consider looking into a library like moment.js to help you manage dates. I drew up a little jsfiddle to demonstrate how I would sort dates using Array.prototype.sort() and Moment.js.

https://jsfiddle.net/1v3dxt6q/

Answer 8 · 2018-05-08T20:19:30Z

May 8, 2018 8:19pm

Impressive! Now I'm no JavaScript expert, so I do have a couple questions. First, how does the function you sorted the dates with work? And second, do you mind explaining what the value of newDate is and what it does?

Answer 9 · 2018-05-11T21:39:48Z

May 11, 2018 9:39pm

Thanks dude

Answer 10 · 2018-05-12T02:27:43Z

May 12, 2018 2:27am

One more question Joseph, when I test your sorting function, the console produces the error "a.diff() is not a function"

Answer 11 · 2018-05-12T20:26:13Z

May 12, 2018 8:26pm

Sorry, completely forgot to post my code lol. Here it is:

window.onload = function() {

let input = document.getElementsByTagName('input')[0];
let buttons = document.getElementsByTagName('button');

let datearr = [];
let date;
let split;
let sortedDates;

  let sorter = function(a, b) {

    if(a.diff(b) > 0) return 1;
    if(a.diff(b) < 0) return -1;
    return 0;
  }

  buttons[0].addEventListener('click', () => {

   date = input.value;
   split = moment(date, "MM-DD-YYYY");


  datearr.push(" " + split);
  alert("Date Added");
  input.value = '';
});

  buttons[1].addEventListener('click', () => {

   if (!datearr[0]) {
    alert('You must input at least one date');
  }

else {

 sortedDates = datearr.sort(sorter);

  if (!sortedDates[1]) {
    document.write("Here is your date: " + sortedDates);
  }

  else {
    document.write("Here are your dates sorted chronologically: " + sortedDates);
  }
}
});
};

Answer 12 · 2018-05-12T21:00:35Z

May 12, 2018 9:00pm

I actually copied all the code out of one of the files in the momentjs library and pasted it in another file in my workspace named moment.js and linked it in to my html file

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How can I do this?

12 Answers

Joseph Wasden

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Joseph Wasden

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Jackson Monk

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Joseph Wasden

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Jackson Monk

Jackson Monk

Jackson Monk

Jackson Monk

Joseph Wasden

Joseph Wasden

Jackson Monk

Jackson Monk

Joseph Wasden

Joseph Wasden

Jackson Monk

Jackson Monk

Jackson Monk

Jackson Monk

Joseph Wasden

Joseph Wasden

Jackson Monk

Jackson Monk

Joseph Wasden

Joseph Wasden

Jackson Monk

Jackson Monk

Jackson Monk

Jackson Monk

Joseph Wasden

Joseph Wasden