How do I make Array.indexOf() case insensitive?

Solution 1:

ES2015 findIndex:

var array = ['I', 'hAve', 'theSe', 'ITEMs'],
    indexOf = (arr, q) => arr.findIndex(item => q.toLowerCase() === item.toLowerCase());

console.log(  indexOf(array, 'i')      ) // 0
console.log(  indexOf(array, 'these')  ) // 2
console.log(  indexOf(array, 'items')  ) // 3

Solution 2:

In ECMA-262, 5th edition, you could use Array.prototype.some for this.

var array = [ 'I', 'hAve', 'theSe', 'ITEMs' ];
var query = 'these'.toLowerCase();
var index = -1;
array.some(function(element, i) {
    if (query === element.toLowerCase()) {
        index = i;
        return true;
    }
});
// Result: index = 2

Solution 3:

Easy way would be to have a temporary array that contains all the names in uppercase. Then you can compare the user input. So your code could become somthing like this:

function delName() {
    var dnameVal = document.getElementById('delname').value;
    var upperCaseNames = names.map(function(value) {
      return value.toUpperCase();
    });
    var pos = upperCaseNames.indexOf(dnameVal.toUpperCase());

    if(pos === -1) {
        alert("Not a valid name");
        }
    else {
        names.splice(pos, 1);
        document.getElementById('canidates').innerHTML = 
        "<strong>List of Canidates:</strong> " + names.join(" | ");
        }
    }

Hope this helps solve your problem.