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JavaScript: Get the human readable format of the given number of milliseconds

JavaScript fundamental (ES6 Syntax): Exercise-230 with Solution

Write a JavaScript program to get the human readable format of the given number of milliseconds.

  • Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond.
  • Use Object.entries() with Array.prototype.filter() to keep only non-zero values.
  • Use Array.prototype.map() to create the string for each value, pluralizing appropriately.
  • Use String.prototype.join(', ') to combine the values into a string.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const formatDuration = ms => {
  if (ms < 0) ms = -ms;
  const time = {
    day: Math.floor(ms / 86400000),
    hour: Math.floor(ms / 3600000) % 24,
    minute: Math.floor(ms / 60000) % 60,
    second: Math.floor(ms / 1000) % 60,
    millisecond: Math.floor(ms) % 1000
  };
  return Object.entries(time)
    .filter(val => val[1] !== 0)
    .map(val => val[1] + ' ' + (val[1] !== 1 ? val[0] + 's' : val[0]))
    .join(', ');
};

console.log(formatDuration(1001));
console.log(formatDuration(34325055574));

Sample Output:

1 second, 1 millisecond
397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds

Flowchart:

flowchart: Get the human readable format of the given number of milliseconds.

Live Demo:

See the Pen javascript-basic-exercise-230-1 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

Checking if a key exists in a JavaScript object?

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined?

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!

You should instead use the in operator:

"key" in obj // true, regardless of the actual value

If you want to check if a key doesn't exist, remember to use parenthesis:

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:

obj.hasOwnProperty("key") // true

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj" Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty: obj.hasOwnProperty("key") // true For performance comparison between the methods that are in, hasOwnProperty and key is undefined.

Ref: https://bit.ly/2CFNp1X