JavaScript's Date Parsing Issue

Question

JavaScript's Date Parsing Issue

I have been working on this specific project on freecodecamp.org and I am determined to complete it without using the moment.js library for assistance:

So far, everything seems to be functioning properly except for one scenario. When the date is formatted in ISO-8601 like this

GET [project url]/api/timestamp/2015-12-25

    app.get("/api/timestamp/:date_string?",function(req,res){
        var date, 
            result = {unix : null, utc: null},
            dateParameter = req.params.date_string;
            console.log("dateParameter:", dateParameter);
        if(dateParameter === ''){
            date = new Date();
            result.unix = date.getTime()*1000;
            result.utc = date.toUTCString();
        }
        else{ 
          try{
            console.log("date_string:", date.dateParameter);
            var dateNumber = parseInt(dateParameter)*1000; // convertion from seconds to milisecond
            date = new Date ( +dateNumber);
            console.log("outer try date:", date.getTime());
          }catch(err){
            try{
              date = new Date(dateParameter + "T00:00:00");
              console.log("inner try date:", date.getTime());
              }catch(err){
                result.unix = null;
                result.utc = "Invalid Date";
                res.json(result);
              }
          }finally{
                console.log("date:", date.getTime());
                result.unix = date.getTime()*1000;
                result.utc = date.toUTCString();
                res.json(result);

              } 

        }
});

However, upon running the code, I am encountering an unexpected outcome of date: NaN. Can anyone spot what mistake I might be making here?

javascript date express

Answer 1

Answer №1

Seeking clarification rather than providing a direct answer, this code snippet may guide you towards a solution.

Here is the current code snippet:

app.get("/api/timestamp/:date_string?",function(req,res){
    var date, 
        result = {unix : null, utc: null},
        dateParameter = req.params.date_string;
        console.log("dateParameter:", dateParameter);

What is the value of dateParameter at this point? If it's '2015-12-25' then this block is skipped. But in case it's '':

    if(dateParameter === ''){
        date = new Date();
        result.unix = date.getTime()*1000;

To ensure correct time measurement, replace multiplication with division as UNIX measures time in seconds while ECMAScript does so in milliseconds:

        result.unix = date.getTime() / 1000;
        result.utc = date.toUTCString();
    }

If dateParameter is a string (like '2015-12-25'), then at this stage date will be undefined since no value has been assigned to it yet. Attempting to call date.getTime() will result in an error.

Next, there is:

    else{ 
      try{
        console.log("date_string:", date.dateParameter);

A reference error should occur leading to the catch block because date is undefined and therefore cannot have a dateParameter property. Using try..catch here is not ideal for JavaScript.

        var dateNumber = parseInt(dateParameter)*1000; // converting from seconds to milliseconds

Given that dateParameter likely represents an ISO 8601 string such as '2015-12-25', the outcome would be the timestamp '1970-01-01T00:33:35.000Z'.

        date = new Date (+dateNumber);
        console.log("outer try date:", date.getTime());

It seems unnecessary to use try..catch again in this scenario. Even if dateNumber results in NaN, the Date constructor still returns a Date object, avoiding an error situation.

I recommend refactoring your code to improve efficiency, especially in handling the else block where operations can be streamlined as shown below:

// Code logic for when dateParameter !== ''
} else {

  if (typeof dateParameter == 'string') {

    // Implement date string validation and conversion to Date object here

    result.unix = date.getTime() / 1000; // Provides UNIX seconds
    result.utc = date.toUTCString();

  } else {
    // Handle cases where dateParameter is not a string
  }

  // Additional operations can follow here
}

PS

Considering the requirement:

An acceptable date string is one that can be successfully parsed by new Date(date_string).

This loose requirement suggests an approach like the following based on the outlined specifications:

app.get("/api/timestamp/:date_string?",function(req,res){
  var date, 
      // Default error message
      result = {error : 'Invalid Date' },
      dateParameter = req.params.date_string;

  // Check dateParameter validity
  if (typeof dateParameter == 'string') {

    // Account for empty strings
    if (dateParameter === '') {
      date = new Date();

    // Validate numerical input
    } else if (+dateParameter == dateParameter) {
      date = new Date(+dateParameter);

    // Proceed with parseable strings
    } else {
      date = new Date(dateParameter);
    }

    // Transform valid Date objects into results or return error
    if (!isNaN(date)) {
      result = {unix : date.getTime(),
                utc  : date.toUTCString()};
    }
  }
  return JSON.stringify(result);
});

Note that post-ECMAScript 2018 standards, the output format of toUTCString follows a consistent pattern "Mon, 09 Jul 2018 02:19:24 GMT".

Answer 2

Seeking clarification rather than providing a direct answer, this code snippet may guide you towards a solution.

Here is the current code snippet:

app.get("/api/timestamp/:date_string?",function(req,res){
    var date, 
        result = {unix : null, utc: null},
        dateParameter = req.params.date_string;
        console.log("dateParameter:", dateParameter);

What is the value of dateParameter at this point? If it's '2015-12-25' then this block is skipped. But in case it's '':

    if(dateParameter === ''){
        date = new Date();
        result.unix = date.getTime()*1000;

To ensure correct time measurement, replace multiplication with division as UNIX measures time in seconds while ECMAScript does so in milliseconds:

        result.unix = date.getTime() / 1000;
        result.utc = date.toUTCString();
    }

If dateParameter is a string (like '2015-12-25'), then at this stage date will be undefined since no value has been assigned to it yet. Attempting to call date.getTime() will result in an error.

Next, there is:

    else{ 
      try{
        console.log("date_string:", date.dateParameter);

A reference error should occur leading to the catch block because date is undefined and therefore cannot have a dateParameter property. Using try..catch here is not ideal for JavaScript.

        var dateNumber = parseInt(dateParameter)*1000; // converting from seconds to milliseconds

Given that dateParameter likely represents an ISO 8601 string such as '2015-12-25', the outcome would be the timestamp '1970-01-01T00:33:35.000Z'.

        date = new Date (+dateNumber);
        console.log("outer try date:", date.getTime());

It seems unnecessary to use try..catch again in this scenario. Even if dateNumber results in NaN, the Date constructor still returns a Date object, avoiding an error situation.

I recommend refactoring your code to improve efficiency, especially in handling the else block where operations can be streamlined as shown below:

// Code logic for when dateParameter !== ''
} else {

  if (typeof dateParameter == 'string') {

    // Implement date string validation and conversion to Date object here

    result.unix = date.getTime() / 1000; // Provides UNIX seconds
    result.utc = date.toUTCString();

  } else {
    // Handle cases where dateParameter is not a string
  }

  // Additional operations can follow here
}

PS

Considering the requirement:

An acceptable date string is one that can be successfully parsed by new Date(date_string).

This loose requirement suggests an approach like the following based on the outlined specifications:

app.get("/api/timestamp/:date_string?",function(req,res){
  var date, 
      // Default error message
      result = {error : 'Invalid Date' },
      dateParameter = req.params.date_string;

  // Check dateParameter validity
  if (typeof dateParameter == 'string') {

    // Account for empty strings
    if (dateParameter === '') {
      date = new Date();

    // Validate numerical input
    } else if (+dateParameter == dateParameter) {
      date = new Date(+dateParameter);

    // Proceed with parseable strings
    } else {
      date = new Date(dateParameter);
    }

    // Transform valid Date objects into results or return error
    if (!isNaN(date)) {
      result = {unix : date.getTime(),
                utc  : date.toUTCString()};
    }
  }
  return JSON.stringify(result);
});

Note that post-ECMAScript 2018 standards, the output format of toUTCString follows a consistent pattern "Mon, 09 Jul 2018 02:19:24 GMT".

JavaScript's Date Parsing Issue

Answer №1

PS

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