连续显示所有 12 个月，但从当前月份开始

Question

I am working on a requirement where I have 12 ion slides and the names of the slides are month names starting from the current month. For ex: If the current month is June, then the name of the first slide should start from June 2020 and go on till May 2021. Well I tried it but not able to achieve. Even if I handle the month, then I am not able to dynamically change the year after December. Here is my code:

my html file

  <ion-toolbar class="toolbars" #ionDragFooter>    
          <ion-title class="ion-text-center">{{currValue}}</ion-title>
  </ion-toolbar>

My.ts file

ngOnInit() {
 swipeNext()
}

 var monthNames = ["January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December"];

  var d = new Date();


if(index == 1){
        var curMn=monthNames[d.getMonth()]+ d.getFullYear();
        console.log(curMn)
        this.currValue=curMn;
      }
      else if(index == 2){
        var curMn=monthNames[d.getMonth()+1]+ d.getFullYear();
        this.currValue=curMn;
      }
      else if(index == 3){
        var curMn=monthNames[d.getMonth()+2]+ d.getFullYear();
        this.currValue=curMn;
}

and so on for all other month. I need to completely automate the month and year starting from the current month. May I know where I went wrong?

Answer 1

You can create a date, then increment the month by 1 eleven times to get 12 months of dates. The month name can be found using toLocaleString with appropriate options.

You need to be careful when incrementing months, eg

let d = new Date(2020,0,31); // 31 Jan 2020
d.setMonth(d.getMonth() + 1) // 31 Feb 2020 -> 2 Mar 2020
d.toDateString();            // Mon Mar 02 2020

So best to set the date to the 1st of the month initially:

 // Optionally provide a date for the starting month function getMonthNames(date = new Date()) { // Copy input date so don't modify it let d = new Date(+date); // Set to 1st of month d.setDate(1); let result = []; // Get 12 month names, starting with current month for (let i=0; i<12; i++) { result.push(d.toLocaleString('default',{month:'long'})); d.setMonth(d.getMonth() + 1); } return result; } console.log(getMonthNames());

Answer 2

To properly change the date you have to increase the date by the amount of months in the date object (in your case d ):

 var d = new Date(); //REM: This will print out the next month, yet d still is unchanged console.log(d.getMonth()+1); console.log(d); console.log('Month did not increase: ', d.getMonth()); //REM: You have to increase your date by one month in the date object d.setMonth(d.getMonth() + 1); console.log(d); console.log('Month did increase: ', d.getMonth()); //REM: By which it will change the year for you, once it is time for it. d.setMonth(d.getMonth() + 11); //REM: +1 from before console.log(d); console.log('Year did increase: ', d.getFullYear());

In your case that would be:

 var monthNames = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]; var d = new Date(); d.setDate(1); //REM: To prevent month skipping. for(var i=0; i<12; i++){ d.setMonth(d.getMonth() + 1); console.log(monthNames[d.getMonth()], d.getFullYear()) };

Some further reading on the issue

Answer 3

This is what I came up with:

const monthNames = ["January", "February", "March", "April", "May", "June",
     "July", "August", "September", "October", "November", "December"];
   
    const today = new Date();
    //gives you year
    const year = today.getFullYear();
    //gives you month as number/index;
    const month = today.getMonth();

    //stores sequenced month names
    const sequencedNames = [];

    //creates June 2020 through December 2020
    for(let i = month; i < monthNames.length; i++) {
        let monthName = monthNames[i];
        sequencedNames.push(monthName + " " + year)
    }
    
    //creates January 2021 through May 2021
    for(let i = 0; i < month; i++) {
        let monthName = monthNames[i];
        sequencedNames.push(monthName + " " + (year + 1))
    }

    console.log(sequencedNames)

Essentially 2 for loops, the first iterating from the current month to the end of the year, and then the second from the start of the year to the current month -- though adding 1 year.