Group array Elements in a sequence JavaScript

August 5, 2022

I am trying to group weekdays together based on the property value in an array. I have used lodash to obtain a solution. My code looks like this,

const array = [{
    weekDay: 'Monday',
    hoursInfo: '11:00am-8:00pm',
  },
  {
    weekDay: 'Tuesday',
    hoursInfo: '11:00am-8:00pm',
  },
  {
    weekDay: 'Wednesday',
    hoursInfo: '9:00am-11:00am',
  },
  {
    weekDay: 'Thursday',
    hoursInfo: '11:00am-8:00pm',
  },
  {
    weekDay: 'Friday',
    hoursInfo: '11:00am-9:00pm',
  },
  {
    weekDay: 'Saturday',
    hoursInfo: '11:00am-9:00pm',
  },
  {
    weekDay: 'Sunday',
    hoursInfo: 'Closed',
  },
];
const result = _.chain(array).groupBy("hoursInfo").value();
document.getElementById("result").innerHTML = JSON.stringify(result);

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"></script>
<div id="result"></div>

I am able to group the list of weekdays which has the same timings together, but my requirement is to group them in a sequence. My expected output is something like this,

Monday-Tuesday: 11:00am-8:00pm
Wedesday: 9:00am-11:00am
Thursday: 11:00am-8:00pm
Friday-Saturday: 11:00am-9:00pm
Sunday: Closed

Please help me with a better approach

>Solution :

Reduce will work

const newArr = array.reduce((acc, item) => {
    if (acc.length && acc[acc.length - 1].hoursInfo === item.hoursInfo) {
      acc[acc.length - 1].weekDay += `- ${item.weekDay}`;
    } else acc.push(item);
    return acc;
  }, [])
  .map(item => `${item.weekDay}: ${item.hoursInfo}`);

console.log(newArr)

<script>
  const array = [
    { weekDay: 'Monday',   hoursInfo: '11:00am-8:00pm' },
    { weekDay: 'Tuesday',  hoursInfo: '11:00am-8:00pm' },
    { weekDay: 'Wednesday',hoursInfo: '9:00am-11:00am' },
    { weekDay: 'Thursday', hoursInfo: '11:00am-8:00pm' },
    { weekDay: 'Friday',   hoursInfo: '11:00am-9:00pm' },
    { weekDay: 'Saturday', hoursInfo: '11:00am-9:00pm' },
    { weekDay: 'Sunday',   hoursInfo: 'Closed'}
  ];
</script>