A simple check if selected, if not add to array in Javascript -

this function supposed take id of selected row , check see if in array or not, if isn't on array, add array, otherwise remove array. problem can't seem order of events right. loop not run way through (because of breaks) if remove breaks, while image changing (checkbox) works, array still wrong.

i don't understand why despite declaring deletestring = []; outside of function, without putting inside function, call of deletestring.push(orderid); fails

it seems obvious problem, on first run regardless of how big array is, whether or not check matches or doesn't match, rest of loop won't run. perhaps should check wait until loop done before using result of found/not-found.

function passselection(orderid) {   // check if empty   if (deletestring.length == 0) {     // turn array     deletestring = [];     // first entry     deletestring.push(orderid);     // mark row checked     $("#"+"select-box-"+orderid).attr('src', 'images/red-checked.png');   }   else {     // not first order     // check if in array     // length of array     var delstrlen = deletestring.length;     // loop through array     (var = 0; < delstrlen; i++) {       if (deletestring[i] == orderid) {         // match found, remove deletestring array         deletestring.splice(i, 1);         // update row         $("#"+"select-box-"+orderid).attr('src', 'images/unchecked.png');         break;       }       else {         // not in array         // add array         deletestring.push(orderid);         // update row         $("#"+"select-box-"+orderid).attr('src', 'images/red-checked.png');         break;       }     }   } } 

you ought use indexof test existence of elements in array. indexof returns position of search-item or -1 if element cannot found so, here code have refactored , tested

var deletestring = []; function passselection(orderid) {   // check if empty   let orderpos = deletestring.indexof(orderid);   if (orderpos == -1) {     // first entry     deletestring.push(orderid);     // mark row checked     $("#"+"select-box-"+orderid).attr('src', 'images/red-checked.png');   }   else {      // match found, remove deletestring array     deletestring.splice(orderpos, 1);     // update row     $("#"+"select-box-"+orderid).attr('src', 'images/unchecked.png');   } }