Blog

To make Array.indexOf() case insensitive in JavaScript, use the Array.findIndex() method with a function that performs a case-insensitive comparison.

Make Array.indexOf() Case Insensitive In JavaScript

For example, given the following array:

var arr = ["a", "b", "c"];

You can use Array.findIndex() to find the index of an element case-insensitively:

var idx = arr.findIndex(function(el) { return el.toUpperCase() === "B"; });

console.log(idx); // 1

If the element is not found, Array.findIndex() returns -1:

var arr = ["a", "b", "c"];

var idx = arr.findIndex(function(el) { return el.toUpperCase() === "D"; });

console.log(idx); // -1

You can use a conditional statement to check if an element exists in an array case-insensitively:

var arr = ["a", "b", "c"];

var idx = arr.findIndex(function(el) { return el.toUpperCase() === "B"; });

if (idx > -1) {

   console.log("element exists at index " + idx);

} else {

   console.log("element does not exist in array");

}

This method is supported in all major browsers except Internet Explorer 11 and earlier.

Array.prototype.findIndex() is an improvement over the traditional for loop because it:

• stops searching once it finds the first element that meets the condition
• doesn’t require a break statement
• works with all types of arrays, including typed arrays
• is available in all major browsers except Internet Explorer 11 and earlier

Note that the function passed to Array.findIndex() must perform a case-insensitive comparison, as the default comparison is case-sensitive.

If you need to support older browsers, you can polyfill or babel.