如果数组数组中的任何项为真或假，如何获取布尔值？

Question

I have this array, which is user generated and changes over time:

const data = [["2020-09-14","15:00","60","Info","April Tucker","Other","yes"],
["2020-09-14","2:00","50","Text","April Tucker","Other","yes"]]

User picks a date which saves to sessionStorage (for example: 2020-11-21): sessionStorage.getItem('date')

Then I use forEach method to know if the first item of array item has the same value:

 const checkForConflicts = () => {
    mydata.forEach((element) => {
      element.includes(sessionStorage.getItem('date'))
    })
  }

If I console log that I get boolean value for all item in the array. How to return only one boolean value, true if checkForConflict returns only false values, or false value if it returned alt least one true value.

Answer 1

It might be that one of either Array.prototype.every or Array.prototype.some or even both brings you the right tool at hand.

... simplified example code ...

 const data = [ ["2020-09-14","15:00","60","Info","April Tucker","Other","yes"], ["2020-09-14","2:00","50","Text","April Tucker","Other","yes"] ]; console.log( 'data.every(item => item[0] === "2020-09-14") ? ', data.every(item => item[0] === "2020-09-14") ); console.log( 'data.some(item => item[0] === "2020-09-14") ? ', data.some(item => item[0] === "2020-09-14") ); data.push( ["2020-09-15","2:00","50","Text","April Tucker","Other","yes"] ); console.log( 'data.every(item => item[0] === "2020-09-14") ? ', data.every(item => item[0] === "2020-09-14") ); console.log( 'data.some(item => item[0] === "2020-09-14") ? ', data.some(item => item[0] === "2020-09-14") );

 .as-console-wrapper { min-height: 100%!important; top: 0; }

Answer 2

Try the some() method:

 const checkForConflicts = () => { mydata.forEach((element) => { element.some(!sessionStorage.getItem('date')) }) }

Answer 3

well you dont need use forEach and loop on the data you can just findIndex of conflicting item -1 mean their is no conflict

const checkForConflicts = () => {
    return data.findIndex((element) => {
      element.includes(sessionStorage.getItem('date'))
    }) !== -1;
  }

Most importantly you have to return value in the function.

Answer 4

I would suggest an array of objects, if not, alter this code to look at the first element in the array of arrays. Note I substituted a local for my test to show it here in a simple manner instead of the sessionStorage

 const data = [{ date: "2020-09-14", time: "15:00", somenumber: "60", cheers: "Info", name: "April Tucker", "note": "Other", says: "yes" }, { date: "2020-09-14", time: "15:00", somenumber: "60", cheers: "Info", name: "Fred Tucker", "note": "Other", says: "yes" }, { date: "2020-09-13", time: "2:00", somenumber: "50", cheers: "Text", name: "April Tucker", "note": "Other", says: "yes" } ]; let testdate = "2020-09-14"; let testdate2 = "2020-09-19"; const checkForConflicts = (item, testme) => { // compare as dates to forgive formatting etc. return (new Date(item).getTime() === new Date(testme).getTime()) }; // I used .filter in case you need to know how many conflicts but .some() might work also let hasConflict = !!data.filter(x => checkForConflicts(x.date, testdate)).length; console.log(hasConflict); let conflictCount = data.filter(x => checkForConflicts(x.date, testdate)).length; console.log(conflictCount); let hasConflict2 = !!data.filter(x => checkForConflicts(x.date, testdate2)).length; console.log(hasConflict2);