I have two arrays
const weekDays = [
{ label: 'Mon', name: 'Monday' },
{ label: 'Tue', name: 'Tuesday' },
{ label: 'Wed', name: 'Wednesday' },
{ label: 'Thu', name: 'Thursday' },
{ label: 'Fri', name: 'Friday' },
{ label: 'Sat', name: 'Saturday' },
{ label: 'Sun', name: 'Sunday' },
];
and const daysOfWeek = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri']
What I wanted to achieve is to move array(daysOfWeek) one item backwards, that is, daysOfWeek = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu'].
To achieve that I created such code
const selectedDaysOfWeek = weekDays.map(({label, name}, index, array) => {
if (daysOfWeek.includes(label)) {
return array[index - 1].label;
}
return ''
});
but it returns label of undefined.
You can simply use Array.prototype.pop() to remove the element from the end and return that element, then use Array.prototype.unshift() to insert an element to the beginning
const weekDays = [
{ label: 'Mon', name: 'Monday' },
{ label: 'Tue', name: 'Tuesday' },
{ label: 'Wed', name: 'Wednesday' },
{ label: 'Thu', name: 'Thursday' },
{ label: 'Fri', name: 'Friday' },
{ label: 'Sat', name: 'Saturday' },
{ label: 'Sun', name: 'Sunday' },
];
const lastElement = weekDays.pop(); // get last element
weekDays.unshift(lastElement); // get new array that last element is first one
let finalResult = weekDays.map(x => x.label) // get only names of week days from object
console.log(finalResult)EDIT: according to the OP's needs
const weekDays = [
{ label: 'Mon', name: 'Monday' },
{ label: 'Tue', name: 'Tuesday' },
{ label: 'Wed', name: 'Wednesday' },
{ label: 'Thu', name: 'Thursday' },
{ label: 'Fri', name: 'Friday' },
{ label: 'Sat', name: 'Saturday' },
{ label: 'Sun', name: 'Sunday' },
];
function getWeeks(arr) {
return [arr[arr.length - 1], ...arr.slice(0, arr.length - 1)];
}
console.log(getWeeks(['Tue', 'Wed', 'Thu']));
console.log(getWeeks(weekDays));I guess your solution is:
const weekDays = [
{ label: 'Mon', name: 'Monday' },
{ label: 'Tue', name: 'Tuesday' },
{ label: 'Wed', name: 'Wednesday' },
{ label: 'Thu', name: 'Thursday' },
{ label: 'Fri', name: 'Friday' },
{ label: 'Sat', name: 'Saturday' },
{ label: 'Sun', name: 'Sunday' },
];
let daysOfWeek = ['Wed', 'Thu', 'Fri']
const firstDayIndex = weekDays.findIndex(day => day.label === daysOfWeek[0]) // get current day index
daysOfWeek.unshift(weekDays[(firstDayIndex || weekDays.length) - 1].label) // add previous day by index
daysOfWeek.pop() // remove last day
console.log(daysOfWeek) // // ['Tue', 'Wed', 'Thu'], here we go
const result = [weekDays[weekDays.length-1],...weekDays.slice(0,weekDays.length-1)].slice(0,5)